The Sea is now a "root zone".
It contains The Briny Deeps, The Brinier Deepers, and The Briniest Deepests.
It has a sub-zone - The Sea Floor
That contains 10 adventure.php areas that unlock via quest progress or buying maps from Big Brother
It has another sub-zone - The Mer-Kin Deepcity
That contains 4 adventure.php areas and The Mer-kin Temple