Vortex
A vortex ability works identically to the whirlwind ability, except the creature gains a swim speed instead of a fly speed, it can form only in a liquid (such as in water), it cannot leave a liquid medium, and it always blocks all vision within it and line of sight past it. In addition, carried creatures must have a swim speed in order to attempt a Reflex save to escape.
Format: Offensive Abilities vortex (4d6+8 B, DC 15, 1/day).
Source
Alien Archive pg. 158