I know of only one written record that tells of cities sunk in the sea in the Americas. It's the Book of Mormon published in 1830. If you read the record you will know that there are more underwater cities down there. The passage below are the words of Christ spoken to an ancient American prophet.
From the Book of Mormon, 3rd Nephi 9:4-8
4 And behold, that great city Moroni have I caused to be sunk in the depths of the sea, and the inhabitants thereof to be drowned.
5 And behold, that great city Moronihah have I covered with earth, and the inhabitants thereof, to hide their iniquities and their abominations from before my face, that the blood of the prophets and the saints shall not come any more unto me against them.
6 And behold, the city of Gilgal have I caused to be sunk, and the inhabitants thereof to be buried up in the depths of the earth;
7 Yea, and the city of Onihah and the inhabitants thereof, and the city of Mocum and the inhabitants thereof, and the city of Jerusalem and the inhabitants thereof; and waters have I caused to come up in the stead thereof, to hide their wickedness and abominations from before my face, that the blood of the prophets and the saints shall not come up any more unto me against them.
8 And behold, the city of Gadiandi, and the city of Gadiomnah, and the city of Jacob, and the city of Gimgimno, all these have I caused to be sunk, and made hills and valleys in the places thereof; and the inhabitants thereof have I bburied up in the depths of the earth, to hide their wickedness and abominations from before my face, that the blood of the prophets and the saints should not come up any more unto me against them.
http://scriptures.lds.org/en/3_ne/9
Something is not right. This message is just to keep things from messing up down the road