Underwater Object Tracking (UOT) is crucial for efficient marine robotics, large scale ecological monitoring, and ocean exploration; however, progress has been hindered by the scarcity of large, multimodal, and diverse datasets. Existing benchmarks remain small and RGB only, limiting robustness under severe color distortion, turbidity, and low visibility conditions. We introduce MUOT_3M, the first pseudo multimodal UOT benchmark comprising 3 million frames from 3,030 videos (27.8h) annotated with 32 tracking attributes, 677 fine grained classes, and synchronized RGB, estimated enhanced RGB, estimated depth, and language modalities validated by a marine biologist. Building upon MUOT_3M, we propose MUTrack, a SAM-based multimodal to unimodal tracker featuring visual geometric alignment, vision language fusion, and four level knowledge distillation that transfers multimodal knowledge into a unimodal student model. Extensive evaluations across five UOT benchmarks demonstrate that MUTrack achieves up to 8.40% higher AUC and 7.80% higher precision than the strongest SOTA baselines while running at 24 FPS. MUOT_3M and MUTrack establish a new foundation for scalable, multimodally trained yet practically deployable underwater tracking.
Figures & tables
Figure 2: MUOT-3M dataset diversity in terms of 16 Phylum categories, 124 families, and 677 fine-grained classes. 16 Phylum categories with corresponding representative families are shown. The distribution and labels of all classes are validated by the expert marine biologist . Non-marine species categories in MUOT-3M, i.e., human-related (diver, scuba) and non-biological (robot, ROVs), are not shown.
Figure 3: Performance degradation of SOTA trackers on WebUOT-1M [ 8 ] and MUOT-3M.
Figure 4: MUOT-3M is much larger than existing UOT datasets.
Dataset
Year
Videos
Classes
Attr.
Min Frames
Mean Frames
Max Frames
Total Frames
Total Duration
Depth Maps
Target Description
Train
Test
UOT32
2019
32
-
-
283
758
1,573
24K
0.27 h
✗
✗
✗
✓
UOT100
2022
104
-
3
264
702
1,764
74K
0.68 h
✗
✗
✗
✓
UTB180
2022
180
-
10
40
338
1,226
58K
0.53 h
✗
✗
✓
✓
VMAT
2023
33
17
13
438
2,242
5,550
74K
0.68 h
✗
✗
✗
✓
UVOT400
2023
400
50
17
40
688
3,273
275K
2.6 h
✗
✗
✓
✓
WebUOT-1M
2024
1,500
408
23
49
733
9,985
1.1M
10.5 h
✗
✓
✓
✓
Table 1: Underwater object tracking datasets. For the attributes provided with a specific dataset, see supplementary, Fig. S7.
Figure 5: MUTrack: Schematic of the proposed multimodal SAM-based tracking pipeline. Step 1 shows the pre-training process of visual-geometric and visual-textual alignments. Step 2 shows the proposed multimodal teacher tracker pre-trained on visual, geometric, and language cues, while Step 3 shows the proposed unimodal student tracker distilling knowledge from the multimodal teacher tracker.
Multimodal
Modalities
MUOT-3M
WebUOT-1M
Teacher (MMT)
I
E
D
L
(success Rate)
(success Rate)
Baseline SAM2 [ 38 ]
✓
×
×
×
60.12
61.11
Baseline SAM2 [ 38 ]
×
✓
×
×
61.20
62.23
Baseline SAM2 [ 38 ]
×
×
✓
×
58.55
59.21
MUTrack-MMT 2
×
✓
✓
×
66.12
65.59
MUTrack-MMT 3
×
✓
×
✓
65.70
63.66
Table 2: MUTrack teacher-only results with baseline SAM tracker. MMT stands for “ Multimodal Teacher ”.
Unimodal
Input
KD Losses
MUOT-3M
WebUOT-1M
Student (UMS)
LVG
LA
LVLA
LM
(Success Rate)
(Success Rate)
MUTrack-UMS
I
✓
✓
✓
✓
66.58
67.10
MUTrack-UMS 1
I
✓
✓
✓
×
64.22
65.31
MUTrack-UMS 2
I
✓
✓
×
✓
64.10
63.96
MUTrack-UMS 3
I
✓
×
✓
✓
64.50
66.09
MUTrack-UMS 4
I
×
✓
✓
✓
63.16
64.77
Table 3: Teacher is fixed and MUTrack student-only results are reported. UMS stands for “ Unimodal Student ”.
Trackers
MUOT-3M
WebUOT-1M
UTB180
UVOT400
UWCOT22
S
P
NP
S
P
NP
S
P
NP
S
P
NP
S
P
NP
MUTrack (MMT)
68.10
69.93
86.66
68.79
70.33
88.20
73.77
74.33
81.69
72.10
75.87
80.67
79.40
81.66
83.22
MUTrack (UMS)
66.58
68.16
84.32
67.10
69.33
86.97
72.88
76.61
80.30
70.55
74.51
78.97
77.87
80.10
81.11
UOSTack
49.22
41.92
61.20
53.14
47.76
65.67
52.67
45.87
68.22
44.25
39.67
56.32
45.31
35.95
53.30
DUTrack
62.66
60.20
79.90
63.81
64.27
81.70
64.61
62.50
83.73
64.16
63.96
80.98
62.08
59.23
75.85
ATC
62.32
60.37
76.50
64.66
65.48
79.10
64.16
65.11
79.43
61.58
63.08
74.47
62.58
61.03
73.93
Table 4: Cross-dataset performance comparison of SOTA trackers: MMT stands for “ Multimodal Teacher ”, UMS is “Unimodal Student”, S is “Success rate”, P is “Precision” and NP is “Normalized Precision”.
Trackers
MUOT-3M
WebUOT-1M
UTB180
UVOT400
UWCOT22
S
P
NP
S
P
NP
S
P
NP
S
P
NP
S
P
NP
MUTrack (MMT)
68.10
69.93
86.66
68.79
70.33
88.20
73.77
74.33
81.69
72.10
75.87
80.67
79.40
81.66
83.22
MUTrack (UMS)
66.58
68.16
84.32
67.10
69.33
86.97
72.88
76.61
80.30
70.55
74.51
78.97
77.87
80.10
81.11
DAM4SAM [ 69 ]
62.33
64.21
75.12
61.10
62.34
70.23
68.10
70.84
76.66
68.97
69.81
74.44
71.12
73.20
80.12
MUTrack (MMT-DAM4SAM)
70.13
71.23
87.33
69.01
72.43
88.32
74.56
75.14
83.61
74.56
76.44
82.34
80.12
82.08
84.61
MUTrack (UMS-DAM4SAM)
68.69
70.32
85.13
66.10
71.40
86.56
73.65
74.46
82.69
73.65
75.14
81.63
79.21
81.80
82.29
Table 5: MUTrack generalization with SOTA Trackers: Our MMT and UMS are plugged into the recent SOTA SAM-based tracking pipelines. MMT stands for “ Multimodal Teacher ”, UMS is “Unimodal Student”, S is “Success rate”, P is “Precision” and NP is “Normalized Precision”.
Figure 6: Performance comparison of MUTrack with SOTA trackers using protocol I and II on MUOT-3M dataset. Norm. stands for “Normalized”.
Appendix figures & tables13 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 7: Overview of the MUOT-3M dataset collection and curation pipeline. The process includes three main stages: large-scale video collection from multiple sources, expert-driven curation to ensure underwater authenticity and visual quality, and annotation with multi-modal data generation. Each stage is standardized to maintain consistency and ensure high-quality tracking sequences across diverse marine environments.
Figure 8: Visualization of the 16 phylum-level classes in the MUOT-3M dataset, showcasing examples from each category alongside their multimodal representations. Each triplet illustrates the RGB frame with bounding box, corresponding depth map, and enhanced image, demonstrating the dataset’s diversity across marine environments and visual conditions. The language annotations describe scene context and species type and behavior, emphasizing the ecological and multimodal richness of MUOT-3M Dataset.
Figure 9: Hierarchical taxonomy of the MUOT-3M Dataset . The diagram illustrates the multi-level organization of MUOT-3M, comprising 16 phylum, 124 families, and 677 fine-grained species. Phylum nodes are shown in green, Family nodes in blue, and fine-grained classes in orange, representing the taxonomic depth of the dataset.
Unimodal
Depth Methods
MUOT-3M
WebUOT-1M
Student (UMS)
MiDaS
Depth Anything
DAC
(success Rate)
(success Rate)
MUTrack-MMT
✓
×
×
66.58
67.10
MUTrack-MMT
×
✓
×
66.12
66.96
MUTrack-MMT
×
×
✓
66.40
67.06
Appendix
Table 6: Influence of depth estimation methods on MUTrack-UMS. The multimodal teacher is fixed, and MUTrack student-only results are reported. UMS stands for “Unimodal Student”
Unimodal
Enhancement Methods
MUOT-3M
WebUOT-1M
Student (UMS)
UTransformer
PixMamba
UVEB
(success Rate)
(success Rate)
MUTrack-MMT
✓
×
×
66.58
67.10
MUTrack-MMT
×
✓
×
66.50
66.93
MUTrack-MMT
×
×
✓
66.52
67.02
Appendix
Table 7: Influence of underwater image enhancement methods on MUTrack-UMS. The multimodal teacher is fixed, and MUTrack student-only results are reported. UMS stands for “Unimodal Student”
Figure 10: Visualization of the 32 tracking attributes defined in the MUOT-3M dataset. Each attribute represents a distinct visual or environmental challenge, covering both generic and underwater-specific conditions. These attributes collectively characterize the full spectrum of appearance and motion variability in underwater tracking scenarios
Visual object tracking follows objects across video frames, maintaining their locations and identities despite motion, occlusion, and changing appearance.
With growing real-world demands, efficient tracking has received increasing attention. However, most existing methods are limited to RGB inputs and struggle in multi-modal scenarios. Moreover, current multi-modal tracking approaches typically use complex designs, making them too heavy and slow for resource-constrained deployment. To tackle these limitations, we propose UETrack, an efficient framework for single object tracking. UETrack demonstrates high practicality and versatility, efficiently handling multiple modalities including RGB, Depth, Thermal, Event, and Language, and addresses the gap in efficient multi-modal tracking. It introduces two key components: a Token-Pooling-based Mixture-of-Experts mechanism that enhances modeling capacity through feature aggregation and expert specialization, and a Target-aware Adaptive Distillation strategy that selectively performs distillation based on sample characteristics, reducing redundant supervision and improving performance. Extensive experiments on 12 benchmarks across 3 hardware platforms show that UETrack achieves a superior speed-accuracy trade-off compared to previous methods. For instance, UETrack-B achieves 69.2% AUC on LaSOT and runs at 163/56/60 FPS on GPU/CPU/AGX, demonstrating strong practicality and versatility. Code is available at https://github.com/kangben258/UETrack.
Ben Kang, Jie Zhao, Xin Chen +5
Dalian University of Technology · City University of Hong Kong
Robust perception is essential for the deployment of autonomous underwater robots. However, optical cameras become unreliable under poor illumination and backscatter. Forward looking (2D) acoustic sensors remain effective under these conditions, but they measure range and bearing while leaving elevation unresolved, creating an ambiguity that prevents individual sonar returns from being localized in three dimensional (3D) space. This complicates the sensor use for 3D scene understanding and precise object detection. We introduce uScenes, a multimodal underwater dataset containing synchronized 3D multibeam sonar point clouds and RGB imagery. The dataset contains 110 scenes and 95,834 synchronized observation, representing 277.6 minutes of data collected across multiple field sessions. uScenes establishes a foundation for underwater sensor fusion, cross modal representation learning and 3D scene understanding. Code and datasets are given at https://github.com/era-research-lab/uScenes.
Trung Tien Dong, Zhenqi Wu, Aditya Penumarti +4
Embodied Robotics and Automation Lab, University of South Florida, Tampa, FL 33610, USA · Mechanical and Aerospace Engineering Department, University of Florida, Gainesville, FL 32611, USA · Naval Architecture and Ocean Engineering at the Seoul National University, Seoul 08826, South Korea
Multimodal visual object tracking can be divided into to several kinds of tasks (e.g. RGB and RGB+X tracking), based on the input modality. Existing methods often train separate models for each modality or rely on pretrained models to adapt to new modalities, which limits efficiency, scalability, and usability. Thus, we introduce OneTrackerV2, a unified multi-modal tracking framework that enables end-to-end training for any modality. We propose Meta Merger to embed multi-modal information into a unified space, allowing flexible modality fusion and robustness. We further introduce Dual Mixture-of-Experts (DMoE): T-MoE models spatio-temporal relations for tracking, while M-MoE embeds multi-modal knowledge, disentangling cross-modal dependencies and reducing feature conflicts. With a shared architecture, unified parameters, and a single end-to-end training, OneTrackerV2 achieves state-of-the-art performance across five RGB and RGB+X tracking tasks and 12 benchmarks, while maintaining high inference efficiency. Notably, even after model compression, OneTrackerV2 retains strong performance. Moreover, OneTrackerV2 demonstrates remarkable robustness under modality-missing scenarios.
Lingyi Hong, Jinglun Li, Xinyu Zhou +6
Shanghai Key Lab of Intelligent Information Processing, College of Computer Science and Artificial Intelligence, Fudan University