Amphibious. Cetus can breathe air and water.
Evasion. If Cetus is subjected to an attack that normally allows a Dexterity Saving Throw for half damage, it takes no damage if it makes a successful saving throw.
Devotion. Cetus gains advantage on saving throws against spells and other magical effects.
Multiattack. Cetus can attack twice instead of once, whenever it takes the Attack action on its turn.
Grab. Whenever the eidolon makes a successful Bite attack, it can attempt a grapple check as a free action. If successful, the eidolon grapples the target. This ability only works on creatures of a size one category smaller than Cetus or smaller.
Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d8 +5 ) piercing damage.
Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) bludgeoning damage.