In Revelation, we are confronted with all the Biblical connotations of numerous images: water, light, fire, clouds, angels, stars, lamps, food, stones, swords, thrones, rainbows, robes, thunder, voices, animals, wings, scavengers, eyes, keys, trumpets, plagues, mountains, winds, seas, altars, blood, locusts, trees, heads, horns, and crowns.
Revelation also presents us with pictures of a Woman, a Dragon, a wilderness, a mark in the forehead, a sickle, pearls, a winepress, a cup of wine, a Harlot, a river, Sodom, Egypt, Babylon, resurrection, a wedding, a marriage supper, the Bridegroom, and the Bride/City in the shape of a pyramid. And then there's the use of symbolic numbers: two, three, four, seven, ten, twelve, and multiples thereof—24, 42, 144, 666, 1,000, 1,260, 7,000, 12,000, and 144,000.
And in all that, you want to pick "seas" disappearing as being literal?
This is why it's necessary to understand the Bible and its use of symbols and patterns if we are ever to understand the Book of Revelation.