Underwater case for Nikon 3100?

I want to expand the things I can do with photography, much appreciated.

A good case for your camera will cost more than the camera ($1, 400 for an Ikelite 6801.31). Unless you want to attempt professional photography in deep conditions, just consider one the waterproof 10Meter depth rated compact cameras.

Make sure you get one of the 10meter rated ones though (Nikon AW100, Canon D20, Olympus 820, etc), as the cheaper ones are not rated as deep, sometimes only to 3 meters. The 10Meter versions usually have additional o-rings and waterproofing that the lower-rated ones do not. In my view, the more the better.

Realize that the depth rating is in static water, so if you find yourself in a raging river with a camera rated to 3Meters, the water pressure could be in excess of the camera's rating. For this reason, a 10Meter rating is highly preferred.

These cameras are not expensive, usually at or less than $300 for the 10Meter rated cameras, and if they become broken - it is far better for it to happen to that camera than your D3100.

And as a side benefit, the cameras are typically ruggedized, and will survive a drop from 5ft, all kinds of banging around, and so on. They are designed to take punishment in the great outdoors.

When I bought my Olympus-8010, what sold me was the demo where the camera was put into video mode, then tossed into a commercial washing machine. It not only was undamaged, but created a cool video.

As previously stated, a good-quality underwater case will cost a ton of money.

A Coolpix AW100 or Powershot D20 would be a good investment.

If you are taking the camera in salt water, be sure to rinse it off with freshwater as soon as you get out of the water.