Mrithun, Lord of the Dark Sea

Drown (Whenever this creature attacks, you may pay {u}. If you do, it gains Deathtouch until end of turn.)
Creatures you control gain drown as long as you
have 5 or more Islands.
{5}{u}{u}: Create a 5/5 creature called Depth Fish
with Drown.
{8}{u}{u}: Sacrifice all Depth Fish creatures and for
each one sacrificed this way, you gain 3 life or an opponent loses 3 life.