I made a video podcast for the project below.
Please check out my other instructables as well.
Step 1: Materials
All you need for this project is:
LED Flashlight (I got 3 for $9 from Home Depot and made 2 dive lights) The lights should also have a push-button switch with a rubber seal and rubber seals at the threaded joints.
A drill with a small bit (I used a 3/64")
A small tupperware container
A small bottle of mineral oil (its a laxative so get it at a pharmacy for a few $)
Step 2: Theory
The first was the movie the Abyss. Remember when they were breathing an oxygenated liquid? This allowed them to go to incredible depths because liquids are not compressible like gasses are (see my video for a slightly more detailed explanation)
The second idea was from looking at pictures of people overclocking their computers. Basically they make their computers run faster than they are supposed to but this causes them to heat up and even melt. One way they combat the heat is to put the computer into an aquarium and fill it with mineral oil. The mineral oil does not conduct electricity or corrode components and just happens to be clear.
So if we can fill a flashlight or other device with oil, we can take the pressure off of the seals, the most work they will do is keeping the oil inside on the surface.