This is a large area with a flooded basin, remnants of a interrupted excavation. There's an NPC here named Sully Mathis who will give you the sidequest “Pull the Plug” if you agreed to help. There's also a cooking station beside the water pump.
From the main gate, there's a trailer van with a sleeping bag, locked chem box, and tool case. There's also a terminal on the table where you can eject Sully's journal.
The trailer to the SW has a Taboo Tattoos on the table.
Lots of Mirelurks, a couple of them 'Glowing'...these will show up after just completing Sully's quest to repair the pumps. You'll need the Aqua Boy/Girl perk for some of the 'work' is underwater.
Some collectible loot like meds, ammo, etc...
I returned to here much later in the game at around level 70, because I had forgotten to pick up the Taboo Tatoo mag...It was full of raiders, some legendary and a couple more mirelurks at the bottom of the pit...