Thaluna, Queen of the Naga

Islandwalk, deathtouch, ward - Sacrifice an Island

Other Snake creatures you control are Merfolk in
additional to other types.

Other Merfolk creatures you control get +1/+1 for
each land with a flood counter on it.

{1}{u}, {ut}: Put a flood counter on target land.
(Lands with flood counters are Islands in
addition to other types.)