Added mobs:

Zombie Villager Drowned:

15% of the drowned can be drowned villager zombies. A zombie villager, sinking into the water long enough, transforms.

Drowned Skeleton:

They are the same as normal drowned but are more likely to spawn with tridents. A skeleton, sinking into the water long enough, transforms.

Creeper Drowned:

It is like a normal creeper but before exploding it poisons its target. A creeper, sinking into the water long enough, transforms.

Husk Drowned:

It is like a normal drowned but it does not burn with the sun. Its attacks apply hunger to the attacked target. A husk, sinking into the water long enough, transforms.

Spider Drowned:

She is fast underwater and there is a chance she will spawn with a rider, they can be: Drowned Skeletons, Drowned Zombie Villagers, or Drowned Wither Skeletons. Its attacks apply nausea to the attacked target.

Drowned Wither Skeleton:

He is fast underwater, and is equipped with a powerful sword capable of slowing down enemies he hits. 
It spawns naturally, though its chance is low.  A wither skeleton, sinking into the water long enough, transforms.

Ender Drowned:

They are very fast underwater. Its attacks apply weakness to the attacked target.

Drowned Piglin:

He is fast underwater and is equipped with a powerful sword capable of poisoning enemies he hits. Its attacks apply fatal poison to the attacked target. Does not spawn naturally. A zombified piglin, sinking into the water long enough, transforms.

Swords added by the addon:

Greatsword Of The Tides: a powerful sword used by drowned wither skeletons. It deals 9 damage, 325 durability, slows the wearer's mobility and attack speed, but slows attacked targets.

Oceanic Sword: a powerful sword used by drowned piglins. It deals 6 damage, 200 durability, poison attacked targets.

Experiments to be activated:

Activate cheats: