Tips for building an underwater self controlled camera apparatus??

have you tried www.makezine.com ?

You can make a fluid filled camera. The fluid being a silicone fluid.

This will be noncompressible and non conducting and you will be able to get near neutral density. A solid state camera is best. The lens will have to be vented so as it changes focus you will not have a compression problem.

A fluid like this will differ from air in optical properties, but you should be able to accomodate easily.

This will allow for a lighter case because no great strength is needed, and in fact it should seal with a membrane to allow for the slight compression at depth.

Power will be either battery or tether power.

Tether power requires care in design. Either use high voltage at low current and include a DC to DC converter to run lights/lens/camera (one for each) or use thicker wire to keep the voltage drop tolerable. If you can design a small controller board that can be dealt with via serial commends = better, but more complex.

You can also use a TV remote control and chip to do this and couple the light to the camera via a light pipe made of multiple optical fibers.

Battery power makes it heavier and larger. It can still use the remote method above, and the batteries can tolerate the silicone fluid.

lithium or nickle metal hydride seems to be the choice, with lithium better at low current performance for longer periods and NiMh having higher currents. Lithium is more complex to charge and more costly, but seems to have the edge if you can design the chagring system

Lights should be LED as they can be immersed in the fluid, but check to make sure there is no air cavity that might crush.

There already exist this type of camera used (and advertised in magazines for) the hydroelectric industry for inspecting penstocks and draft tubes. For fresh and salt water applications.

Go to www.hcipub.com and in the click on the "Product Directory", search "camera" and you will find a list of underwater robot camera makers with links to there wesbites.

The kind I was going to build isn't built yet either.

A mini ROV? or a micro version?

I suggest you contact an organization like the Woods Hole Oceanographic Institution. They are up on the latest commercial and custom made technologies. It is always lower cost to bootstrap off existing technologies than to develop new ones on your own. Once you establish contacts at an organization, you may want to travel there to explore concepts in greater detail (Cape Cod is lovely this time of year).