When an enemy moves within 5 feet of you, you may use your reaction to spit ink at their eyes. The enemy must succeed on a Dexterity saving throw against a DC of 8 + your proficiency modifier + your Dexterity modifier. On a failure, they are blinded for one round. Once you've used this ability, you cannot use it again until you've finished a Long Rest.

This ability grants you advantage on Stealth checks to hide. If you are wearing no clothing or armor and carrying no items, you may make a Stealth check to hide even when a creature could normally see you. Both of these abilities are lost if you move or take an action. You may use a Sleight of Hand check to conceal a small weapon or item on your person while hiding in plain sight at the discretion of your DM.

You can breath both air and water.

+2 to strength 

A monster with Darkvision can see in the dark within a specific radius. The monster can see in dim light within the radius as if it were bright light, and in Darkness as if it were dim light. The monster can’t discern color in Darkness, only Shades of Gray. Many creatures that live Underground have this Special sense.

You do not need a free hand to grapple an enemy. If you start your turn with an enemy grappled, you may choose to deal bludgeoning damage to that enemy equal 1d12 plus your Strength modifer, as you constrict it with your powerful tentacles

This disks can be manipulated by the cecaelia to create a suction powerful enough to suspend the creature out of water, as well as grip opponents with frightening strength. Though prehensile enough to manipulate objects, the tentacles do not possess the manual dexterity or speed required to use weapons effectively. You gain advantage on Athletics checks made to climb and to either initiate or end a grapple. You may take the Use an Object action as a bonus action on your turn and may due so at a range of up to 10 feet

Their lower body’s support structure is composed entirely of vessels that can be filled and emptied of fluid, allowing them to stretch, manipulate, expand, and contract their entire body. You gain resistance to bludgeoning damage. In addition, you may squeeze through spaces up to two size categories smaller than you with no penalties. Weapons, armor, and other items must also fit through the space to use this ability. For the purposes of this ability, size categories smaller than Tiny (2 1/2 ft square) equal one-half the previous category. For example, a medium cecaelia may move through spaces as small as 2 1/2 ft square with no penalties and 1 ft square with normal penalties.