Stock view finders on camcorders typically don’t cut the mustard underwater. They are designed to have the eye placed right up against them to be useful. Underwater, the camera is in a housing, and the operator is wearing a diving mask, so the eye ends up too far away to effectively use the camera’s view finder.
Housing manufacturers have come up with several solutions to work around this problem. One is to fit the housing itself with a view finder magnifier. This simply magnifies the camera’s stock view finder making it easier to see underwater and through a diving mask. This is a relatively inexpensive solution. However, you generally need to put your mask right against the housing to see the image.
Another relatively cheap solution is to utilize the camcorders built-in flip-out LCD monitor. Some housings are made big to accommodate the extended LCD monitor protruding from the side of camera. The negative in this approach is that the housing’s volume increases substantially and greatly increases its buoyancy. Since housings should be slightly negatively buoyant underwater, these designs require the housing to be loaded with lots of weights or ‘ballast’ to normalize their buoyancy. This might be OK while diving, but out of the water, it makes for a very heavy video system that’s cumbersome to handle and transport.
The best solution to this problem is to have an external LCD monitor specifically designed for underwater video. Some external monitors are in their own watertight housings and connect to the top of the video camera’s housing. These are called top-mounted external monitors. They have the advantage of adjustable viewing angles. A disadvantage is requiring waterproof cables and connectors to route the video signal from the camera housing to the monitor housing. Also, a top-mounted monitor greatly increases the bulkiness and drag of the whole system underwater, and its vulnerable to snagging on things.
A less expensive and more streamlined approach is to locate the external monitor at the inside rear of the video camera housing. This avoids the need for waterproof cable assemblies and connectors and introduces no increased drag or bulkiness. The sacrifice is the lack of adjustable viewing angle. However, some LCD monitors have a range of viewing that is quite sufficient even with the monitor in a fixed position.