The Outpost 29 Sealed Vault is underneath the outpost command nowadays and for the most part is completely unknown by outsiders to even exist. The vault can still be sealed shut and is usually kept so.
Its location was first gleamed from a half drunk sailor by a local barman(who was a Dep7 agent). Further talking resulted in more solid details and a great deal of storyland. The barman reported this story and all the others he heard for that day to his boss who figured there might be something to it and further questioned the drunk. The drunk revealed the location of the vault he has seen when diving and that it was relatively isolated. A agent was dispatched in the general direction with orders to check the area(multiple stories were being checked at the time). 6 mts later an agent finally made it to the location and conducted some dives and found the building under quite a depth of water. Having found it to be still apparently sealed he sent message to Bunker Command eventually which resulted in a Technology Recovery Team being sent to investigate. They then requested further Recovery teams and a security team or two as Bunker Command had determined there was valuable information and computers in the vault.
The recovery operation consisted of the construction of a temporary base of operations and the gradual building of a seawall and pump house to pump the water out. There were some setbacks, such as a wall collapse and numerous raider attacks. The attacks resulted in Settlement sending security teams to purge the area for several miles around of any hostiles.
Several working computers and vast amounts of data in the form of a computerised library was recovered from the vault, as well as painting and works of art.
Vault is assumed to have been constructed by a wealth individual who wanted to create a sort of time capsule.