Hello!
An idea to address a common issue, as well as provide new content:
Diving while swimming, and the ability to move small distances underwater. This will present 2 functions:
1) Diving removes your hitbox and conceals your character, but at the cost of increased stamina consumption. This means, in desperate times, you can swim under and away from players trying to boat-block you and kill you without murder using hitbox jankery.
You can swim under boats but coming into contact with land/shallow water will make you resurface. This could fix a lot of hitbox river deaths. Whether this makes you character invisible like the mole/boreworm or just gives a dark shadow outline of your character, up to you.
2) Unique forageables; like special curio shells or special sand, fish, crabs and lobster and crawfish, seaweed curio/garden green, clams and other sea creatures, and of course: Pearls. I mean the guy on the pearl diver credo is diving.
The main drawback is a far larger stamina consumption, and maybe even double damage per asphyxiation tick while dived.
Not sure exactly how to make it happen, maybe right click on water while swimming and select "Dive!", or maybe the speed icons change to a little diving man when in the water, or have it be a toggle that appears when swimming is on.