Lake Mead Cave

The entrance to Lake Mead Cave is underwater. Northeast of Ranger Station Alpha on the other side of the lake is a partially submerged boat. This boat is red and the bow is sticking out of the water. By swimming under the boat on its west side you can follow the cliff down to the cave entrance. This cave is just a touch southeast of the Crashed B-29. The easiest way to find it is to go to Callville Bay. There is a boat ramp that faces southeast and has a nonoperational harpoon gun. Follow the angle of this boat ramp and swim out into the lake that direction, pass over the bomber to get to the cave. Many shopping carts can be found scattered throughout the exit of the cave along with unopenable boxes and sunset sarsaparilla boxes.

Layout
The cave is split into two major sections. The first section has an above-water surface that can be used to regain oxygen, and to regain health by drinking the rad-free water. The majority of the first area is underwater, and near the left wall in this section there are several crates of ammo, and two first aid kits to loot. There is a small opening low to the wall at the edge that leads to the second section. The second section has no way to regain oxygen, so a rebreather is highly suggested. The body of a person who appears to have met an unfortunate end lies near the center, along with a few suitcases, various loot, and a concrete block near their torso.

Loot
Just inside the cave are a few ammunition boxes and a Sunset Sarsaparilla crate. Almost directly to the left upon entering to the main area of the cavern, at the base there are also a few boxes of medical supplies, ammo boxes (one containing .45-70 Gov`t), metal boxes, and filing cabinets. Exploring further in might prove difficult without the rebreather, as the rest is under water. If you do however, you will find a skeleton with three suitcases full of pre-War money and another ammunition crate. Also, you can find a Lad's Life magazine near the suitcases too. The skeleton and his/her suitcases are littered with casino chips, and the concrete block that the objects are sitting around suggest the person met an unfortunate end at the hands of somebody after winning a good deal of money.
 * exactly how many ammo boxes are near the entrance? on i find three metal boxes, two first aid kits, and two file cabinets (one of which is empty), and none of these containers had any .45-70 gov't ammo in them. someone please verify... ~kev~

Appearances
appears in Fallout: New Vegas.