Indoor swim meets are challenging because pools are dim, humid, and often have ugly mixed lighting. Shoot RAW so you can correct difficult white balance later. Use a fast shutter speed—about 1/250s or faster if possible—along with AI Servo/continuous autofocus and burst mode to catch action.

Be ready to raise ISO substantially on the 50D, even to 3200 or higher if needed. Your current lenses may feel slow indoors, so if available, a faster telephoto or prime would help, but you can still work with what you have by watching your shutter speed carefully.

Learn the strokes and time your shots: each stroke has moments where the face and arms look strongest. Try different angles from deck level and the stands, and don’t forget a few wider shots for atmosphere.

Protect your gear from humidity and splashes; keeping it dry isn’t the only issue, since humid pool air can also affect equipment. If your lens has a panning mode, it may be useful.

Flash is generally not a great choice here unless you know it’s allowed and won’t distract swimmers, so rely on available light first.