Thanks for the all the related thread: took a while to read - answered many questions and raised a few more.
The Hugycheck leak detector looked interesting.
It is a bit than a leak detector (I usually think of those as things that blink or sound when water is in already
) it is something to help make sure no leaks exist prior to the water.
Are leak detectors useful?
Yes, though more when it is a small leak, massive leak and the detector is probably toast also
(Thinking of leak detectors that flash etc. Things like the Hugyfot are really cool to me)
If so are they available for Aquatica.
Not sure if they came out with a system AFAIK. Hugyfot and Gates (video) have systems, not sure about others.
Does the Aquatica take a tripod?
Backscatter has one now that they developed
If TTL is to be used with the flash system is there a special option I need to request?
Ikelite has built in TTL with Ikelite strobes, the other housings may need extras, either different bulkheads and or electronics (such as the external Sea & Sea option or Heinrichs) and you will need to look how each housing can be configured for TTL
On settings UW I guess for most wide angles people use F8 and above, but what is a normal ISO and what is the maximum ISO.
It varies based on lighting and other factors. Not sure how high anyone shot the 5D underwater, but people have mentioned shooting up to 1600 (do not recall if it was only above water) and liking the results. You really need to shoot and decide for yourself what you find acceptable in terms of noise, but the camera has a pretty broad range that you will be able to use well. I have a tendency to use lower ISOs (usually set it to the lowest ISO on the camera) though many have been shooting 200/400/800 (with a variety of cameras) and reporting good results.
What about glass domes vs plastic which is most common?
Glass is usually more expensive and heavier. I would guess alot of that will be answered based on budget and the level of photographer. People get very good shots with both.