White balance will do litle to correct for that kind of light and shooting under water. Tiffen filter has one of the more complete choices of correction filter for such conditions. Both Adorama and B&H have pretty full offerings, but you can also query Tiffen directly at their web site: http://www.tiffen.com/filters.htm

I miss spoke regarding in the pool. I meant that the kids will be in the pool. I'm not getting in that water, no way. I'll be on the deck taking photos of the kids in the water during practice. Sorry for the confusion.

Any way....

I took a stop by there tonight. No camera as I was on my way home from work. I have Mercury vapor lights in the pool and flourescent in the lobby. The lighting in the pool area is plenty bright.

Use the camera's White Balance Preset, taking your reading off a surface you know to be neutral - a gray card is ideal, but anything else that is neutral is fine. Do a test shot to make sure that it is to your satisfaction. If there is a colour cast, it is possible that the surface chosen for the setting is not really neutral, so try something else until you reach a satisfactory balance.

If you are shooting JPEGs, accurate white balance is very important. However, if you are able to shoot RAW, extremely accurate adjustments can be made in processing. RAW is much more flexible in every way. If you have a reasonably large CF card, you can also set the camera to save both a JPEG and RAW version of each exposure. If your processing skills do not include RAW now, you can use the JPEGs and later revisit the RAW files, once your skills are up to speed.

Even though it may be bright in there, it would probably be wise to set the camera to ISO800. It provides a nice balance between high shutter speed and acceptable noise levels. Shoot on aperture priority using the widest apertures your lens allows. This will guarantee the highest shutter speed no matter where you point the lens.

Do check your exposures - the camera seeks a middle tone average. If the pool area is mostly bright white, it may cause the swimmers to be underexposed. Use your Exposure Compensation to set for ideal skin tones.

Test shots and the review function are your best friends. Use them whenever anything changes, to fine tune your results. Once you have the ideal settings, you can always delete the test exposures. Don't wait until the event is over and you are at home to discover that you needed to adjust your settings.

Larry,

A digital camera's white balance only adjusts on the red-blue color temperature axis, and therefore will not compensate for the multiple spectral spikes in the illumination produced by mercury vapor and industrial fluorescent lighting sources.

I had issues with this and tried the custom white balance using an Expodisc and was very, very pleased with the results. Even though there was a mixture of lights, including Merc. Vapor, the color was nicely balanced and required no adjustments on a calibrated monitor. There are many people who will say that a coffee filter works just as well, but to me, I like having a high level of percision that's consistent from job to job.