I feel like sunken chests are being very underused now. They have a unique aspect of being able to be carried around which is something regular chests can't do. Due to space limitation on boat, chests are usually deployed last and if something on the boat gets destroyed, you would have to hammer down chests to place this something again (because chests block the placement). Hereby, I have few suggestions on how to make sunken chests valuable even after they have been raided.
- Allow unlocking chests with key instead of hammering them. Key can either be craftable or purchasable from hermit crab. Deer antlers can be used as key too.
- Remove collision box. This is most important, as long as sunken chests restrict movement they are no competition to normal chests.
- Allow accessing chest contents while carrying them in body slot once they have been unlocked.
- Allow chests to be "upgradable" with minisigns - so you don't have to dig and redeploy the sign every time you move its chest around. 1 hammer hit on upgraded sunken chest will cause the sign to fall off.
- Make sunken chests visually as large as normal chests - because they have 9 slots too.