1 Introduction  
‘Sit, be still, and listen.’  
2 Background  
2.1 Atmospheric Scattering Model  
2.2 Simplified Model  
2.3 Revised Model  
3 Deep Underwater Image Enhancement Algorithms  
3.1 Encoder-Decoder Models  
3.2 Modular Designs  
3.3 Multi-Branch Designs  
3.4 Depth-Guided Networks  
3.5 Dual Generator GANs  
3.6 Network Specifics  
4 Experimental Settings  
4.2 Evaluation Metrics  
4.3 Benchmark Results  
5 Future and Emerging Directions  
6 Conclusion