Naiad.

These mysterious aquatic creatures dwell in the unseen depths of lakes, rivers and grottos. They like to hide in their underwater caves and avoid contact with anyone who lives on land, but sometimes late at night, you can see their scaly skin flickering in the moonlit waters.

If you're lucky, you'll be able to catch them in the lakes and rivers of Ishdagar. 

Naiad are coming soon in the next update.