Merciless Tide

If the battlefield is flooded, tap all creatures you don't control. They don't untap during their controller's next untap step. Otherwise, the battlefield becomes flooded until end of turn. (All lands are Islands in addition to their other types for as long as the battlefield is flooded.)
"I wonder how Ethama can capture the beauty of the sea in a still image, yet allows me to listen to the crashing shores in this piece... "
-Kiora