You jumped in from the top? I don't remember where that goes, but if you're trying to complete the vault, water and locked terminals are the key. There's submerged parts that, if you don't have enough science (75) you have to dive down into those submerged parts and find dead ghoul technician bodies and loot them for the passwords. Those passwords unlock the terminals which unlock parts of the vault with the final goal being the overseer's office and the armory (sweet loot here).
If you're trying to leave? Look for the vault door and keep traveling upwards.