Originally posted by awaldram Unless you can get deckside, 200mm is only just usable for 25m pool shooting.
In a 50M pool which if the OP's daughters are serious will be where there out (or will be) then 300mm is an absolute Min ...
Here in the south, 50m pools are for Long Course ( summer ), Short course is the rest of the year, and is normally a 25 YARD pool. My girls swim year round, so they do both. Many of the long course venues here are outdoors so deck access is not an issue and 70-200mm works fine, you don't even need an expensive f/2.8 lens.
For indoors, often the deck is closed to all but swimmers and coaches, so unless we are lucky enough to get deck access, we generally don't bother to shoot the action, Many of these indoor venues seem to have lighting comparable to caves and you really need f/2.8, and longer lenses at 2.8 are cost prohibitive when you are shooting just for fun.