Machine Learning for the Internet of Underwater Things: From Fundamentals to Implementation
Organizations: James Watt School of Engineering, University of Glasgow, Glasgow, United Kingdom
Abstract
The Internet of Underwater Things (IoUT) is becoming a critical infrastructure for ocean observation, marine resource management, and climate science. Its development is hindered by severe acoustic attenuation, propagation delays far exceeding those of terrestrial wireless systems, strict energy constraints, and dynamic topologies shaped by ocean currents. Machine learning (ML) has emerged as a key enabler for addressing these limitations, offering data driven mechanisms that enhance performance across all layers of underwater wireless sensor networks. This tutorial survey synthesises ML methodologies supervised, unsupervised, reinforcement, and deep learning specifically contextualised for underwater communication environments. It outlines the algorithmic principles of each paradigm and examines the conditions under which particular approaches deliver superior performance. A layer wise analysis highlights physical layer gains in localisation and channel estimation, MAC layer adaptations that improve channel utilisation, network layer routing strategies that extend operational lifetime, and transport layer mechanisms capable of reducing packet loss by up to 91 percent. At the application layer, ML enables substantial data compression and object detection accuracies reaching 92 percent. Drawing on 300 studies from 2012 to 2025, the survey documents energy efficiency gains of 7 to 29 times, throughput improvements over traditional protocols, and cross layer optimisation benefits of up to 42 percent. It also identifies persistent barriers, including limited datasets, computational constraints, and the gap between theoretical models and real world deployment. The survey concludes with emerging research directions and a technology roadmap supporting ML adoption in operational underwater networks.
Figures & tables
| Function | Traditional Approach | ML-Based Approach |
|---|---|---|
| Channel Estimation | Analytical models, pilot symbols | Neural network prediction, adaptive [ 34 ] |
| Power Control | Fixed levels, lookup tables | RL-based adaptation [ 35 ] |
| MAC Protocol | Fixed backoff, TDMA slots | Learning-based scheduling [ 43 ] |
| Routing | Shortest path, geographic | Q-learning, GNN-based [ 44 ] |
| Localisation | ToA/TDoA algorithms | DNN regression, RL-aided [ 55 ] |
| Stage | Layer Type | Output/Kernel |
|---|---|---|
| Encoder | Conv ReLU | 64 filters, |
| MaxPool | ||
| Conv ReLU | 32 filters, | |
| MaxPool | ||
| Dense | 16 units | |
| Decoder | Dense | 32 units |
| Stream | Layer / Action | Parameters |
|---|---|---|
| Sonar | Conv2D 3 | 32, 64, 64 filters |
| Kernels | , , | |
| Strides | 4, 2, 1 | |
| Sensor | Dense 2 | 128, 64 units |
| Joint | Concatenate | Fusion of streams |
| Dense | 512 units |
| Layer Type | Filters | Kernel / Pool |
|---|---|---|
| Conv3D + BN | 32 | |
| Pool3D | - | |
| Conv3D + BN | 64 | |
| Pool3D | - | |
| Conv3D + BN | 128 | |
| Pool3D | - |
| Category | Technique | Primary Applications | Key Advantages |
|---|---|---|---|
| Supervised Learning | k-NN, SVM | Modulation classification, vessel identification | Robust with limited data [ 42 ] |
| Random Forests | Fault detection, routing decisions | Interpretable, handles mixed features [ 74 ] | |
| Gaussian Processes | Field estimation, path planning | Uncertainty quantification [ 56 ] | |
| Unsupervised Learning | k-Means, DBSCAN | Network clustering, topology organisation | Adapts to irregular deployments [ 78 ] |
| PCA, Autoencoders | Data compression, anomaly detection | 50–1000 compression [ 64 ] | |
| Reinforcement Learning | Q-Learning, DQN | MAC protocols, power control, routing | Learns from interaction [ 44 ] |
| Survey Reference | Year | Primary Scope | Key Contributions | Limitations |
|---|---|---|---|---|
| ML in Wireless Sensor Networks (General) | ||||
| Alsheikh et al. [ 65 ] | 2014 | ML algorithms in terrestrial WSNs | Comprehensive ML taxonomy, algorithm comparison, complexity analysis | No underwater considerations, outdated ML techniques |
| Kumar et al. [ 66 ] | 2019 | ML techniques for WSN optimisation | Energy efficiency focus, clustering algorithms, fault detection | Minimal underwater content, lacks deep learning |
| Klaine et al. [ 136 ] | 2017 | Self-organising networks with ML | SON paradigm, cellular focus, optimisation techniques | Terrestrial only, no acoustic channels |
| Underwater Communications and Networking | ||||
| Li et al. [ 12 ] | 2019 | High reliability in UWSNs | Protocol comparison, reliability metrics, cross-layer design | No ML techniques discussed |
| Application | Baseline | ML Method | Improvement |
|---|---|---|---|
| Physical Layer | |||
| Localisation | Trilateration | CNN | 7 accuracy |
| Channel Est. | LS Pilot | LSTM | 15 dB MSE gain |
| Modulation Class. | Energy Det. | ResNet | 25% @ -5 dB SNR |
| MAC Layer | |||
| Channel Access | ALOHA | Q-learning | 45% throughput |
| Task | Method | Metric | Value | Ref. |
|---|---|---|---|---|
| Localisation | Trilateration | Error | 8.5 m | [ 145 ] |
| -NN | Error | 1.2 m | [ 120 ] | |
| CNN | Error | 0.8 m | [ 55 ] | |
| Channel Est. | LS Pilot | MSE | -5 dB | [ 22 ] |
| CNN | MSE | -15 dB | [ 34 ] | |
| LSTM | MSE | -20 dB | [ 76 ] |
| Algorithm | BER @ 0 dB | Train | Infer. | Mem. |
|---|---|---|---|---|
| MMSE Equalizer | N/A | 0.5 ms | 10 KB | |
| RLS Adaptive | N/A | 2.0 ms | 25 KB | |
| MLP (3 layer) | 2 h | 5.0 ms | 150 KB | |
| CNN (5 layer) | 8 h | 12 ms | 500 KB | |
| LSTM | 24 h | 20 ms | 1.2 MB | |
| Transformer | 48 h | 35 ms | 4.5 MB |
| Feature | This | Jan. | Khi. | Chr. |
|---|---|---|---|---|
| Full protocol stack | ✓ | – | – | |
| Deep learning coverage | ✓ | – | ||
| Reinforcement learning | ✓ | – | ✓ | |
| Federated learning | ✓ | – | – | – |
| Cross-layer analysis | ✓ | – | – | – |
| Quantitative repository | ✓ |
| Method | Mean Err. | 95% Err. | Latency | Robustness |
|---|---|---|---|---|
| Trilateration | 8.5 m | 22 m | 10 ms | Poor |
| Weighted LS | 6.2 m | 18 m | 25 ms | Fair |
| Particle Filter | 3.8 m | 11 m | 200 ms | Good |
| -NN ( =10) | 1.2 m | 3.5 m | 15 ms | Excellent |
| CNN | 0.8 m | 2.2 m | 50 ms | Excellent |
| DQN Active | 0.5 m | 1.5 m | 100 ms | Excellent |
| Application | Metric | Traditional | ML-Based | Improvement | ML Technique |
| Physical Layer | |||||
| Localisation | Position Error (m) | 8.5 | 0.8 | 91% reduction | CNN |
| Channel Estimation | MSE | 0.043 | 0.012 | Significant reduction | LSTM |
| Modulation Classification | Accuracy @ 0 dB | 75% | 96% | 28% increase | CNN |
| Adaptive Modulation | Throughput (kbps) | Baseline | +20–45% ∗ | Substantial increase | DQN |
| MAC Layer | |||||
| Operation | Traditional | ML-Based | Savings |
|---|---|---|---|
| Acoustic Transmission | 10 J/pkt | 0.34 J/pkt | 29 |
| Channel Estimation | 0.5 J/est | 0.08 J/est | 6 |
| Route Discovery | 45 J/route | 2.1 J/route | 21 |
| Object Detection | 8.2 J/frame | 0.15 J/frame | 55 |
| Network Maintenance | 850 J/day | 12 J/day | 71 |
| Total Daily | 2800 J | 180 J | 1556 |
| Task | Traditional | ML-Based |
|---|---|---|
| Training/Setup Phase | ||
| Localisation Setup | ||
| Routing Table | ||
| Channel Model | ||
| Inference/Operation Phase | ||
| Position Estimation | ||
| Application Domain | Metric | Traditional | ML-Based | Improvement | ML Technique | Reference |
| Physical Layer | ||||||
| Localisation | Position Error (m) | 8.5 | 0.8 | 91% reduction | CNN | [ 168 ] |
| Channel Estimation | MSE | 0.043 | 0.012 | Significant reduction | LSTM | [ 151 ] |
| Modulation Classification | Accuracy @ 0dB SNR | 75% | 96% | 28% increase | CNN | [ 169 ] |
| Adaptive Modulation | Throughput (kbps) | Baseline | Improved | Substantial increase | DQN | [ 170 ] |
| MAC Layer | ||||||
| Operation | Traditional | ML-Based | Savings | Ref. |
|---|---|---|---|---|
| Acoustic Transmission | 10 J/packet | 0.34 J/packet | 29 | [ 186 ] |
| Channel Estimation | 0.5 J/estimate | 0.08 J/estimate | 6 | [ 151 ] |
| Route Discovery | 45 J/route | 2.1 J/route | 21 | [ 176 ] |
| Object Detection | 8.2 J/frame | 0.15 J/frame | 55 | [ 179 ] |
| Network Maintenance | 850 J/day | 12 J/day | 71 | [ 78 ] |
| Total Daily Energy | 2800 J | 180 J | 15.6 | — |
| Condition | Metric | ML Gain | Reference |
|---|---|---|---|
| High node mobility | PDR | +45% | [ 188 ] |
| Sparse topology | Delivery ratio | +38% | [ 29 ] |
| High traffic load | Throughput | +67% | [ 155 ] |
| Time-varying channel | BER | -52% | [ 170 ] |
| Low SNR ( 0 dB) | Classification | +28% | [ 169 ] |
| Multi-hop (5+ hops) | Latency | -41% | [ 164 ] |
| Task/Algorithm | Traditional | ML-Based |
|---|---|---|
| Training/Setup Phase | ||
| Localisation Setup | ||
| Routing Table Creation | ||
| Channel Model Fitting | ||
| Clustering Initialisation | ||
| Inference/Operation Phase | ||
| Algorithm | RAM | Flash | Inference | Platform |
|---|---|---|---|---|
| Q-Learning Router | 12 KB | 48 KB | 0.3 ms | Cortex-M4 |
| DQN Router | 64 KB | 256 KB | 2.1 ms | Cortex-A53 |
| LSTM Predictor | 128 KB | 512 KB | 5.4 ms | Jetson Nano |
| CNN Classifier | 256 KB | 1.2 MB | 8.7 ms | Coral TPU |
| Dijkstra (100 nodes) | 40 KB | 8 KB | 12.3 ms | Cortex-M4 |
| AODV (100 nodes) | 120 KB | 24 KB | 45.7 ms | Cortex-M4 |
| Operation | Traditional | ML | Hardware |
|---|---|---|---|
| Channel Estimation | 450 mJ | 72 mJ | ARM Cortex-M4 |
| Route Computation | 890 mJ | 23 mJ | ARM Cortex-A53 |
| Object Detection | 8200 mJ | 150 mJ | Jetson Nano |
| Anomaly Detection | 340 mJ | 45 mJ | Coral TPU |
| Packet Scheduling | 125 mJ | 18 mJ | ARM Cortex-M4 |
| Cluster Formation | 560 mJ | 85 mJ | ARM Cortex-A53 |
| Protocol Comparison | Improvement | Network Size | Reference |
|---|---|---|---|
| QELAR vs VBF | 20% longer | 100 nodes | [ 176 ] |
| DEKCS vs LEACH | 70% longer | 200 nodes | [ 78 ] |
| EDORQ vs DBR | 35% longer | 150 nodes | [ 191 ] |
| Q-EAVAR vs QELAR | 25% longer | 100 nodes | [ 192 ] |
| ENCRQ vs QHUC | 23.5% longer | 200 nodes | [ 177 ] |
| CTRGWO vs LEACH | 23.5% longer | 150 nodes | [ 193 ] |
| Performance Dimension | Typical Gain | Maximum Reported |
|---|---|---|
| Localisation accuracy | 5–10 | 99.98% accuracy |
| Throughput | 1.5–2.5 | 148% increase |
| Energy efficiency | 6–70 | 1556 |
| Network lifetime | 1.5–3 | 173% extension |
| Scalability (500 nodes) | 3–4 PDR | 265% advantage |
| Inference latency | 2–20 faster | vs |
| Deployment Scenario | Data Strategy | Update Strategy | Learning Strategy | Key Considerations |
|---|---|---|---|---|
| Short-term ( 1 month) | Pre-collected | None required | Pre-trained only | Minimise complexity |
| Medium-term (1–12 months) | Transfer learning | Differential updates | Online adaptation | Balance adaptability vs. stability |
| Long-term ( 1 year) | Active learning + synthetic | Hierarchical federated | Continual learning | Prevent catastrophic forgetting |
| Deep sea ( 1000m) | Synthetic + few-shot | Physical recovery only | Edge learning | Extreme isolation constraints |
| Mobile (AUV-based) | Opportunistic collection | Gossip-based | Collaborative learning | Exploit mobility for updates |
| Challenge Category | Specific Challenge | Recommended Solution | Expected Outcome |
|---|---|---|---|
| Resource Constraints | Limited processing | TinyML, quantisation, pruning | 10–100 speedup |
| Memory limitations | Model compression, tiling | 4–32 reduction | |
| Energy budget | Adaptive duty cycling, hierarchical inference | 85 energy reduction | |
| Environmental | Biofouling | Fouling-aware training, online calibration | 85% accuracy at 3 months |
| Corrosion | Predictive maintenance, redundancy | 87% failure prediction | |
| Pressure effects | Depth-aware models | 92% accuracy maintained |
| Technology | Near-term (1–2 years) | Mid-term (3–5 years) | TRL | Key Enablers |
|---|---|---|---|---|
| Physics-Informed NN | Broadband acoustic modelling, Single-domain PINNs | Multi-physics coupling, Real-time deployment | 4–5 | GPU acceleration, Automatic differentiation |
| Transformers | UATR classification, Signal denoising | End-to-end communication, Multi-modal fusion | 5–6 | Sparse attention, Model compression |
| Graph Neural Nets | Secure routing, Trust modelling | Dynamic topology learning, Distributed inference | 4–5 | Efficient message passing, Edge deployment |
| Federated Learning | Privacy-preserving training, Model aggregation | Asynchronous underwater FL, Byzantine robustness | 4–5 | Communication-efficient protocols |
| Meta-Learning | Few-shot environment adaptation | Continual meta-learning, Zero-shot deployment | 3–4 | Diverse training environments |
| Semantic Comm. | Task-specific compression, Meaning encoding | LLM-guided semantics, Generative decoding | 3–4 | Edge-optimised LLMs, Diffusion models |
| Challenge Category | Key Problem | Research Direction | Potential Impact |
|---|---|---|---|
| Data Scarcity | Million-dollar datasets | Self-supervised learning, PINNs | 100 reduction in data needs |
| Interpretability | Black-box decisions | Physics-grounded explanations | Enable regulatory approval |
| Real-Time Processing | Computational gap | TinyML, neuromorphic computing | 100 efficiency improvement |
| Adversarial Robustness | Natural/intentional attacks | Physics-constrained defences | Maintain 95%+ accuracy under attack |
| Federated Learning | Communication constraints | Hierarchical FL, compression | Enable collaborative training |
| Maintenance | Model drift in isolation | Continual learning, self-healing | Extend deployment 3–5 |
| Layer | Application | Traditional Performance | ML Performance | Key Enabling Technique |
|---|---|---|---|---|
| Physical | Localisation accuracy | 8.5 m error | 0.5–0.8 m error | CNN, DQN active sensing |
| Channel estimation MSE | 0.043 | 0.012 (significant reduction) | LSTM temporal modelling | |
| Modulation classification | 75% @ 0 dB SNR | 96% @ 0 dB SNR | CNN feature learning | |
| Adaptive modulation throughput | Baseline | +20–45% (substantial gain) | DQN policy optimisation | |
| MAC | Channel utilisation | 8% | 18–42% (scenario-dependent) | Q-learning adaptive backoff |
| Collision rate | 45/hour | 12/hour (73% reduction) | Multi-agent RL coordination |
Appendix figures & tables9 assets
Supplementary material from the paper’s appendix.
Appendix
| Application | Best ML Method | Key Advantages | Constraints | Data Requirements | Accuracy |
| Physical Layer | |||||
| Localisation | CNN + k-NN | Sub-metre accuracy, robust to multipath | High memory for fingerprints | 1000+ fingerprints | 0.8-1.2m |
| Channel Estimation | LSTM + PINN | Predictive capability, physics-consistent | Computational complexity | 100-1000 samples | MSE: 0.012 |
| Modulation Classification | CNN | Robust at low SNR | Requires diverse training | 5000+ per class | 96% @ 0dB |
| Adaptive Modulation | DQN | Handles outdated CSI | Large state space | 1000+ episodes | 20–45% gain |
| MAC Layer | |||||
| Algorithm Class | Memory | FLOPS | Power (W) | Latency (ms) | Recommended Platform |
| k-NN | O(nd) | O(ndk) | 0.01-0.1 | 10-50 | ARM Cortex-M4 |
| Decision Trees | O(nodes) | O(depth) | 0.01-0.05 | 1-10 | Any microcontroller |
| SVM | O(n_sv × d) | O(n_sv × d) | 0.05-0.2 | 5-20 | ARM Cortex-M7 |
| Small CNN (¡5 layers) | 100KB-1MB | 10-100M | 0.1-1 | 10-100 | ARM Cortex-A53 |
| Medium CNN (5-20 layers) | 1-10MB | 100M-1G | 1-5 | 50-500 | NVIDIA Jetson Nano |
| Large CNN (¿20 layers) | 10-100MB | 1-10G | 5-20 | 100-1000 | NVIDIA Jetson Xavier |
| Operation | Traditional (J) | ML-Based (J) | Improvement | Battery Life Gain | Key Technique |
|---|---|---|---|---|---|
| Acoustic Transmission | 10 per packet | 0.34 per packet | 29× | Weeks → Years | Adaptive power, Q-learning |
| Channel Estimation | 0.5 per estimate | 0.08 per estimate | 6× | 3 → 18 months | CNN prediction |
| Route Discovery | 45 per route | 2.1 per route | 21× | Days → Months | GNN, caching |
| Object Detection | 8.2 per frame | 0.15 per frame | 55× | Hours → Days | YOLOv8n, pruning |
| Network Maintenance | 850 per day | 12 per day | 71× | 3 → 214 days | Predictive, federated |
| Data Compression | 2.0 per MB | 0.02 per MB | 100× | 10 → 1000 days | Autoencoder |
| Technology | Complexity | TRL | Time to Deploy | Risk Level | Primary Challenges |
| Ready for Deployment (TRL 7-9) | |||||
| k-NN Localisation | Low | 8 | 1-3 months | Low | Training data collection |
| Q-Learning MAC | Medium | 7 | 3-6 months | Low | Parameter tuning |
| CNN Channel Est. | Medium | 7 | 3-6 months | Medium | Model size, real-time |
| Decision Tree | Low | 9 | ¡1 month | Very Low | Limited capability |
| Pilot Testing (TRL 4-6) | |||||
| Application | Min. Samples | Ideal Samples | Collection Method | Augmentation Strategy | Cost Estimate |
|---|---|---|---|---|---|
| Localisation | 500 | 5,000 | Grid survey | Noise injection, multipath | $50K-200K |
| Channel Estimation | 100 | 1,000 | Continuous recording | Doppler, time-varying | $20K-100K |
| Object Detection | 1,000 | 10,000 | ROV survey | Colour, turbidity, rotation | $200K-1M |
| Species Classification | 50/class | 500/class | Opportunistic + targeted | Pitch shift, time stretch | $100K-500K |
| Anomaly Detection | 1,000 normal | 10,000 normal | Long-term monitoring | Synthetic anomalies | $50K-200K |
| Protocol Learning | 100 hours | 1,000 hours | Passive recording | Noise, interference | $20K-50K |
| Layer 1 | Layer 2 | Optimisation Method | Performance Gain | Key Insight |
|---|---|---|---|---|
| Physical | MAC | Joint channel-access learning | 35% efficiency | Channel predicts collision probability |
| Physical | Network | Channel-aware routing | 40% reliability | Route around poor channels |
| MAC | Network | Traffic-aware clustering | 45% energy | Cluster based on communication patterns |
| MAC | Transport | Queue-aware scheduling | 60% latency reduction | Prioritise based on transport needs |
| Network | Transport | Congestion-aware routing | 50% throughput | Route around congested nodes |
| Network | Application | Content-aware routing | 30% bandwidth | Different paths for different data types |
| Environmental Factor | Impact on ML | Adaptation Strategy | ML Technique | Success Rate |
|---|---|---|---|---|
| Biofouling | Sensor drift, degradation | Progressive calibration | Online learning, EWC | 85% maintained |
| Temperature Variation | Model accuracy drop | Multi-temperature training | Domain adaptation | 90% maintained |
| Pressure (Depth) | Component behaviour change | Depth-stratified models | Ensemble methods | 92% maintained |
| Turbidity | Optical degradation | Robust features | Attention mechanisms | 86% maintained |
| Seasonal Changes | Distribution shift | Continual learning | Progressive networks | 88% maintained |
| Node Mobility | Topology changes | Dynamic retraining | GNN, online RL | 91% maintained |
| Investment Area | Initial Cost | Annual OpEx | Benefit/Year | ROI Period | 5-Year NPV |
|---|---|---|---|---|---|
| Data Collection | $1-5M | $100K | - | - | -$5.5M |
| Model Development | $0.5-2M | $200K | - | - | -$2.5M |
| Hardware Upgrade | $5-50K/node | $10K/node | - | - | -$100K/node |
| Training/Personnel | $200K | $100K | - | - | -$700K |
| Energy Savings | - | - | $50K/node | Immediate | $200K/node |
| Maintenance Reduction | - | - | $100K | Year 1 | $400K |
| Scenario | Network Size | Duration | Budget | Use ML? | Recommended Approach |
|---|---|---|---|---|---|
| Short-term monitoring | ¡10 nodes | ¡1 month | ¡$100K | No | Traditional protocols |
| Coastal surveillance | 10-50 nodes | 3-12 months | $100K-1M | Partial | ML for critical functions |
| Long-term monitoring | 50-200 nodes | ¿1 year | $1-10M | Yes | Full ML stack |
| Ocean observatory | ¿200 nodes | Permanent | ¿$10M | Essential | Advanced ML + federation |
| Research deployment | Any | Variable | Limited | Yes | Transfer learning |
| Commercial aquaculture | 20-100 nodes | Continuous | $500K-5M | Yes | Proven ML solutions |