Island Realms DLC - Water World

I feel an excellent addition to the DLC list would take place in/near the ocean. The first level starts on the beach, the secret level a beach-side, water-logged, cave, and the final level takes place in an "Ocean Monument".

Mobs:

Drowned - Similar to a "Zombie" but faster and with a configurable chance to be holding a "Trident" (see below).

Puffer fish - Deals small amounts of damage with a chance of poison.

Swashbuckler - The skeletons of dead pirates, they have cutlasses, do a lot of damage, and are slow. 

Captain - Similar to the "Necromancer" except he summons "Swashbucklers" instead of "Zombies".

Guardian - Acts like guardians from "Minecraft" with a ranged attack and the chance to lower the player's attack speed temporarily.

Boss:

Elder Guardian;

Attacks; 

Laser Beam: Uses the classic guardian beam to slow and damage the player.

Charge: Swims quickly towards the player after a short backwards motion, if it hits the player it does a lot of damage.

Call: Calls/Summons guardians.

Weapons:

Trident: Has a mid-range attack where the trident is sent straight forward in a thrusting motion, can also be equipped in the bow slot to be thrown under water.

Unique Variant: Poseidon's Scepter; Increases the player's under water movement speed.

Pincer: A crab-like attachment to the arms allowing the player to slice the enemies in  2 quarter circles (one for each arm alternating)

Features:

- Swim Animations 

- 50% lightning attack boost under water.

- Slower Projectiles under water