- Time: The easiest way to track how far you have gone is to not worry about distance and instead just track how long you are in the pool. Swimming for 30 minutes is much easier to figure out than counting the laps.
- Count Lengths: Rather than counting laps, you can try counting lengths. It is a little easier to keep track of lengths because you always know that swimming in one direction will be an odd number and swimming in the other direction will be an even number. It is a little easier to figure out if you are length 12 or 14 than if you are on lap 6 or 7.
- Wrist Watch: A very easy way to count laps is to wear a water proof or water resistent wrist watch and to click the lap counter function every lap. You then have an accurate count without having to worry about keeping it straight in your head. I prefer not to wear a watch when I swim, but I keep a watch at the end of the pool where I get in and every 250 meters (5 laps) I click it. I only need to count to 5 each time, and I know basically how long that will take me, so I can click the watch then and have it count my sets out rather than the individual laps.
- Goggles: Even easier than using a wristwatch, you could get a set of goggles that automatically counts your laps for you through the use of a small compass and displays the lap count and duration of your swim on the lens of the goggles. I’m not sure if these are even on the market yet, though.
- Lane Dividers: My main method for counting laps is to use the lane dividers, usually combined with my wristwatch for every 5 laps. What I do is I push the buoys on the lane divider away from the wall when I get in, and then move one towards the wall for each lap that I complete before starting the next one. When I get to 10, I start pushing them back out away from the wall. This is a simple and handy method that is available in most pools.
- Set Workouts: You could write up a set workout that you are going to follow in the pool so that you do not need to track how many laps that you swim. Instead, you would follow the workout as outlined and you would know how far you are going to swim before even getting in the pool. For example, a workout might be written to swim 5 laps as a warm up, 5 sets of 100 meters (2 laps each), and then 5 laps as a cool down. You only have to track where you are in your workout, and not every single lap that you have gone.
- Lap Times: You can track individual lap times or multilap times throughout the swim to get an average of how long it takes, and then just divide the amount of time you swam by your average lap time to get an estimate of how far you swam. (This method provided by Nat in the comments on Wes‘s site.)
- Coach: You could find a friend or a coach that will count your laps for you and let you know how you are doing.
- Letters: Instead of counting laps, use letters and words. Start at “A”, and think of words that begin with “A” on the first lap. On the second lap, think of words that begin with “B”. If you are swimming more than 25 or 26 laps, then just start over and count how many times you get through the alphabet.
Those are the methods that I can think of off of the top of my head. Did I miss any?