Fig. 1. Structure of cycle-consistent adversarial network

Fig. 2. Structure of improved cycle-consistent adversarial network

Fig. 3. Structure of generator network

Fig. 4. Structure of discriminator network

Fig. 5. Device diagram of underwater microscopic imaging system

Fig. 6. Absorption spectra of typical seawater and blue-green dye inks

Fig. 7. Some self-made target images

Fig. 8. Results of underwater self-made target images processed by different algorithms

Fig. 9. Comparison of underwater natural stone images processed by different algorithms