StiX floats are the easiest way to lighten up a heavy DSLR system underwater. Made by 4th Generation Systems, they are easy to put on and can be cut away as necessary.
At some point or another, underwater photographers are likely to experience a low-battery warning during a dive. Hopefully it occurs towards at the end of the dive, but for those of us unfortunate enough, the warning kicks in early and we end up carrying around a dead camera. Thankfully, there are plenty of ways to improve the camera’s battery life so that dreaded low-battery warning doesn’t ruin your dive.