Amphibious. The Yaraga can breathe air and water.

Master of the Seas. Yaragas can move under and around watercraft as though it were not difficult terrain.

Slippery. Due to it's eel like body and slick hide, the Yaraga is immune to grapples. 

Multiattack. The yaraga makes two attacks: one with its bite and one with its tail.  

Bite. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 26 (3d12 + 7) piercing damage. Target must make a DC 18 strength saving throw or become grappled. If a creature is grappled, the Yaraga may not make a bite attack. 

Tail. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 26 (3d12 + 7) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or be pushed up to 10 feet away from the dragon turtle and knocked prone.

Storm of Waves(Recharge 5–6). The yaraga swings it's tail creating a massive wave in a 60-foot cone. Each creature in that area must make a DC 18 Dex saving throw, taking 30 (10d6) bludgeoning damage on a failed save and knocks the creature prone, or half as much damage on a successful one. Any creatures in the water automatically fail the save. Deals max damage to vehicles