What a marvellous piece of kit the GoPro Hero range of action cameras is. They have an application for almost any activity and especially suitable for anything with any appreciable amount of risk that might destroy a more conventional camera. It doesn't matter whether you are skiing, riding a bike, taking selfies as a tourist or jumping off a tall building with nothing more than a wing-suit. No wonder they have proved to be the most popular Christmas present of 2014. Naturally, at Ocean Leisure Cameras we maintain a large stock of accessories and it goes without saying that many of our customers want to take their GoPro Hero 4 with them when snorkelling or scuba diving. The standard housing is good for 40m deep and if you want to go deeper there's a tougher diving housing available too. It's simple to bolt a GoPro Hero 4 to a bike but once you go under water, the characteristics of light conspire to make it more difficult to get good footage. It matters little whether you use a GoPro Hero 4 or a Red Epic camera that costs many thousands of pound, the physics remain the same. Firstly, you need to keep your camera steady if your material is going to be watchable. We thoroughly recommend some sort of handle and one that can be made neutrally buoyant will be best. You neither want your precious Go Pro Hero 4 to float off nor to drop away to great depths. If you are doing some dare-devil activity, you'll be happy with whatever you record but underwater you'll want to be very much more selective. An LCD screen that shows what the camera sees is essential. The Silver Edition of the GoPro Hero 4 comes already equipped but in order to keep the retail price as attractive as possible, the much higher quality Hero 4 Black Edition (it will shoot 4k video and also will run at a higher frame-rate to smooth out the action) does not. However, an economically priced LCD screen is available for the Black Edition that plugs straight into the camera and it comes with the fatter back door for the housing to accommodate it. Water absorbs light but it does it selectively. The warmer wavelengths of light, the reds and the yellows, get filtered out first so that as you go deeper, everything starts to look very blue. You can make the most of the red and yellow light that penetrates the water in the first 15-metres by filtering out some of the blue. The GoPro Hero 4 has such a wide-angle lens that, although a flat red filter will work, a domed filter will be more effective over the whole width of the image and sharpness won't suffer at the edges. If you want decent colour when you go deeper, there's no escaping the fact that you will need to take some white light with you in the form of some lamps. The same applies whatever camera you shoot with. Still cameras can use flash but for live action you need a constant source of light. A diving torch will not give light that is even enough. It will be patchy but not only that, the GoPro Hero 4 will try to look into the shadows leaving the lit parts burn-out. You need video lights. Ocean Leisure Cameras has a selection available at a range of prices. Check that part of this web-site for more details. What else do you need? A spare battery and charger will come in useful. That battery can be charging while you are under water with your GoPro Hero 4 and be ready for the following dip under water.