Here are five tips to help you shave time off your open-water swims:
1. Practice with a purpose: During open-water practice, try repeats of swimming out and back instead of relying solely on long, non-stop swims. Completing a 4x500 (swimming 250 meters out and 250 meters back, four times) can help with necessary open-water skills such as turning/swimming around buoys, navigation, and getting in and out of the water. You'll also be more likely to bump into people unintentionally, which helps prepare for the inevitable contact found in open-water events.
2. Draft: Practice drafting with other swimmers just as you would practice drafting on your bike. You may gain some speed, you'll get used to swimming with others in close proximity, and you won't have to look up to sight quite as much. It's still best to be responsible for your own positioning and do your own sighting to confirm where you're going.
3. Straight as an arrow: Learn to swim straight. Most swimmers have a stronger side and prefer breathing to one side -- both of which can send you off on an angle, fast. Practice regular sight-breathing in the pool as well as in open-water practice. Start by looking up every 8-10 strokes, and gradually work up to 20.
4. By the buoy: Turning directly next to buoys in open-water events may not be your ticket to a faster time. Avoid the inevitable slowing with all the crowds next to the buoy by swimming just a bit wider. You'll save overall time and avoid much of the kicking and thrashing that is common at the turns.
5. Peel rubber: If you plan to wear a wetsuit for triathlons or other open-water swim races, practice, practice, practice getting your wetsuit off. Experiment with what works best for you to facilitate quick and easy removal. Many swimmers like to "pre-treat" their legs with a petroleum-free roll-on protectant used to prevent chafing, or with a fat-free cooking spray.