Swimming is a very interesting sport to photograph, it is simultaneously easy and quite difficult. What I mean by this is the you have so many opportunities to get shots of your subjects because there are multiple swimmers all swimming multiple times. At the first meet I went to there were 3 schools and at least 30 athletes or more participating. Swimming is also not a very fast sport, nor is there any change in direction other then swimming up and down your lane. As a photographer you will always know where your subject is headed and can anticipate that, unlike many other sports.
Ideally when shooting swimmers you want to get there face and possibly cap in the shot because without that many shots just don’t look right. The difficulty with that is that swimming has many different strokes, some that make it easy to get a shot of the swimmers face like Breast stroke and Butterfly stroke. However, strokes like the Freestyle can be quite difficult to get a shot of the swimmers face since it only comes up once every few strokes and usually only on on side for a second or two, not to mention the water thrashing all over.
Another way that swimming is unlike many other sports there is water involved and a lot of it. You don’t realize until looking at your pictures later on how water can make or break a shot.
My settings for shooting swimming are typically a shutter speed of 1/800 or more, f/stop 2.8, an ISO ranging from 1000-3200 depending on the venue, white balance usually set to white fluorescent lighting, auto focus set to AI Servo, and High Speed Continuous shooting. Although I said before that swimming is not a fast sport, you’ll want to have a high shutter speed because of all the splashing water and quick movement of arms and legs.