Hmmm . . . someone correct me if I'm wrong, but those two plants in the middle look like 'Brazilian Swords', which are actually peace lilies (Spathiphyllum sp.) and will eventually die if left under water. They make great houseplants, though!
I agree, they look like Peace Lilies to me, too. And IME they'll do OK underwater for a while, but eventually will die unless their leaves are allowed to grow up out of the water.