Merfolk can magically morph their fins and tail into legs, or vice versa back into half-fish form, with a full-round action. They can move and fight in water as well as a flying creature can in open air when they are in their half-fish form.
Siren Song (Racial Power)
As a move action once per battle, you can sing a beautiful melody reminiscent of a gentle sea breeze, or a mournful dirge that carries the portent of tidal waves. Until the end of your next turn, all nearby allies add the escalation die to their defenses, OR all nearby enemies subtract the escalation die from their defenses (your choice).
Champion Feat: Using your siren song is now a quick action.