Wave Strider

Innate Spellcasting. The Strider can cast the following spells, requiring no material components.

At Will: Water Breathing, Water Walk

Regeneration. The Strider regains 10 hit points if it starts its turn with at least 1 hit point, is touching water, and didn't take fire damage after its last turn. The Strider dies only if it ends its turn with 0 hit points and doesn't regenerate.

Infused Weapons. The Strider's weapon attacks deal an additional 2d8 damage when the Strider is in water (included in its attacks).

Spellcasting. The Strider is a 10th level spellcaster (spellcasting ability Intelligence, Spell Save DC 16, +8 to hit with spell attacks). The Strider has the following Wizard Spells prepared:

Cantrips (At Will):  Acid Splash, Dancing Lights, Frostbite, Mage Hand, Shape Water 

1st Level (4 Slots): Absorb Elements, Fog Cloud, Sleep, Shield

2nd Level (3 Slots): Melf's Acid Arrow, Mirror Image, Misty Step    

3rd Level (3 Slots): Haste, Tidal Wave, Wall of Water

4th Level (3 Slots): Control Water,  Ice Storm, Polymorph

5th Level (2 Slots): Cone of Cold, Wall of Force

Multiattack. The Strider makes two weapon attacks

Trident. Melee or Ranged Weapon Attack, +7 to hit, reach 5 ft. or range 20/60, one target. Hit: 6 (1d6+3) piercing damage or 7 (1d8+3) piercing damage if used with two hands to make a melee attack, plus 9 (2d8) damage if the Strider is in water.