I’ve seen it quite a few times now, some photographers just use too much grease on the o-rings. There might be the myth that the grease is preventing water from entering the housing, but that’s not the case – it’s the o-ring! Yes, the o-ring stops the water from getting in the housing and the grease just helps the o-ring to stay smooth and flexible. The more grease you put on the o-ring, the more likely it is for things like tissue, fibers, sand, dust etc. to stick on, and cause a leak on the sealing surface of the o-ring! Use only a tiny amount of grease (use the grease recommended by the manufacturer) and pull the o-ring through your fingers to spread the grease evenly all over. That way you can also feel if there is any sand or damage on the o-ring. For cleaning the o-ring I normally use my T-shirt, but a tissue or microfiber cloth works just fine as well.
Empty or no batteries at all inside the strobe or camera, no memory card in camera, hot-shoe not connected, housing buttons not lined up, auto-focus not switched on, lens-cap still on camera, etc. – Every single one of these minor problems can quickly turn into a big frustration underwater, because you’re not able to fix it without opening the housing! Eliminate all that by simply taking a test shot after setting up your camera equipment and before going diving. Make it a habit to take a test shot of your lens-cap and you will instantly see if everything is working fine – if not, you’re still able to fix it before you go diving!
I often get asked how I get such steady footage on my videos – Having good buoyancy skills helps, but the only recipe for steady macro video is using a tripod! I use this cheap and easy DIY setup (made out of Locline elements) but there are many different options for tripods out there to choose from.