I've been playing the mod for a long time and something that is missing is the presence of new mobs in the water. For years I've dreamed of the presence of sea kings and more sea creatures on the high seas so I decided to make the suggestion already containing some ideas.
sea cow: a beast from the seas with the appearance of a cow, it can be tamed after taking damage from the player, it appears in Nami's arc and is very cute lol.
Giant squid: a giant squid that appears inside the laboon.
king of the seas: the kings of the normal seas.
Lord of the Coast: the king of the seas who made Shanks lose his arm.
merman pirates: merman pirates with a remade skin, having fins, increased size and speed in the water.