Red filter?

[jleech]

There are some specialty filters out there specifically formulated for taking pictures underwater.  The exact color is guarded, as these companies make money by selling the filters at a premium fee.  Most are some shade of magenta I believe.

UR/PRO is one of the companies that sells specialty filters.  To be fair, the filters really aren't much more expensive than any other quality filter for a camera.  They have versions for tropical blue-green water, and green/algae water (Fresh & salt) 

I've had a filter that Ikelite provided with my first UW housing for my digital still camera.  It was some shade of magenta, and was made to go over the lens port of the housing.  I actually never used it in water it was designed for - tropical blue-green water.  I tested it a couple of times, and found that it blocked too much light for the shots I primarily was taking, which were mostly local.

I found a couple of good and simple steps in photoshop that did the majority of cleanup.

I would like to play with a filter in tropical, since most pictures there are done using ambient light, and there is usually abundant light, even down at 80-100 ft.

One of the drawbacks to filters, is that you should compensate for white balance using the filter.  This is reasonably easy to do at the camera for some setups, for others you may need to take a picture of something with white or grey in the field of view, then use that setting to balance the rest of your shots in a photo processing tool like photoshop.

Most people just let the camera do the best it can, with or without a filter, and then color correct in something like photoshop.

  For most 30-50 ft dives in tropical locations, you are probably in the heart of what the filter was designed for, so shouldn't have to make any real corrections

Underwater photography can be a lot of fun, but it can also can get very confusing and complex if you let it.

My recommendation would be to not worry too much about a filter, and just take a lot of pictures!  The best part about digital is you can take as many pictures as you want, and it doesn't cost any more than just taking 1.

For tropical diving, you probably can't go too far wrong with one of the commercial filters.  If you do decide to get a filter, try some with and without the filter so you get a feel for what the filter is doing for you.

Either way I'll be jealous, because you'll be diving somewhere warm, and I'll still be in MN.

Jeff

P.S.  I hope I didn't confuse you too much!