Decals:

Collect the following decals to unlock the corresponding effect. They are listed in order from left to right and top to bottom.

1. No decal: Default.
2. Anchor: Halves damage taken from collisions with the environment. (3 required)
3. Octopus: Halves damage taken from enemy torpedoes. (3 required)
4. Skull and Crossbones: Halves damage taken from enemy depth charges. (3 required)
5. Arrow through Heart: Halves damage taken from collisions with enemy vessels. (5 required)
6. Swords and Shield: Halves damage taken from mines. (5 required)
7. Wooden Ship: Quadruples recovery speed at the water's surface. (5 required)
8. Bomber: Halves damage taken from enemy air-to-sea bombs. (3 required)
9. Snail: Reduces damage taken from all sources. (7 required)
10. Orca: Halves air consumption rate of the masker. (3 required)
11. Lobster: Prevents submarine hull leaks. (5 required)
12. Bull: Increases torpedo damage. (7 required)
13. Golden Falcon: Increases maximum forward/reverse speed. (10 required)
14. Sea Serpent: Increases maximum dive/surface speed. (7 required)
15. Eye: Reveals enemy positions on the sea chart. (5 required)
16. Tridents: Increases torpedo reload speed. (7 required)
17. Lightning: Increase torpedo travel speed. (5 required)
18. Crescent Moon: Extends the mission time limit by 60 seconds. (5 required)
19. Scope Orb: Extends post-mission Periscope Strike by 10 seconds. (7 required)
20. Cherries: Extends post-mission Periscope Strike by 20 seconds. (10 required)
21. Sun: Increases torpedo speed in post-mission Periscope Strike. (10 required)
22. Panther: Decreases enemy speed in post-mission Periscope Strike. (10 required)
23. Crown: Lowers the health of enemy bosses. (10 required)
24. Scorpion: Negates the effect of water currents. (5 required)
25. Squid: Increases the effect of waters currents. (3 required)
26. Sea Horse: Halves the effect of water currents. (3 required)
27. Penguin: Halves the impact of shock waves. (7 required)
28. Wave: Unknown.
29. Frog: Increases the impact of shock waves (3 required)
30. Fire: Increase the amount of bubbles created by your torpedoes. (3 required)
31. Mario: Homing torpedoes. (10 required)
32. Whale: Unknown.