Minecraft is a game that from its version 1.13 implemented improvements to the ocean. Adding fish, algae, seagrass, turtles, dolphins, etc. Today I come to propose a new mob the rajiformes:
It is found rarely in coral reefs and more commonly in the depths of the seas.
Life: 21 health points.
Damage: Bite 2.5. Sting 1.5 + poison.
Hidden under the sand if the player accidentally touches or steps on one of these rajiformes will begin to be attacked with the sting of the mob poisoning the player (duration of 1:30 level 2). Then he will continue attacking him with his mouth and sometimes with the sting. When he is under life he tries to hide from the player.
This part was difficult for me but I found a drop that is not bad at all. From 0-2 Nautilus Shell with 6% obtaining (java edition) and 8% (bedrock).
I was also thinking that instead of leaving a Nautilus Shell I could give a new item: stripe fins with which to create pants that increase the speed of the player when swimming.
I hope you liked my suggestion.