I bought a knitting row counter (pic below, $1.99 at JoAnn Fabrics) to wear on a cord while I swim, to count laps.

Today the lifeguard asked me what I was wearing and what I was using it for (he saw me fiddling with it between laps).

I showed it to him, and told him where I'd gotten it, and he thought it was so cool.

This is what it looks like (it's hollow like a spool, so you can thread a cord through it, and wear it around your wrist or neck, or pin the cord to your swim suit)

That's a really great idea! If I ever take up swimming I can use my row counter to keep track. Multipurpose!

Great idea! I'm thinking about how else that could be used in exercise. I bet there are lots of possibilities....

I use those for knitting, they're great! esp if the pattern is a little more complicated.

Great idea!

I've been meaning to pick one up to help with more complicated patterns, but I'd probably forget to use it for an easy row, then lose track of where I actually am...that said, it actually seems better suited for your idea!

I think people could use it at gyms for keeping track of sets, especially beginner-folk that don't have a routine developed.

Great tool! Neat!

I decided to use it for the pool, because I have short-term memory and memory retrieval problems due to my fibromyalgia (and or the medications I use to control it).

One small distraction, and my short-term memory is wiped (I'm like Dorey in Finding Nemo).

I would be mentally rehearsing the lap number in my head, and a stray thought would wipe it out.

I used to have an almost photographic memory, so it's really weird and disturbing to need assistance. I could just swim and not count, but I do like being able to gauge my progress.

Oh my, why didn't I think of that? My pool is outdoors and I was literally moving small rocks from one pile to another I was trying to think of something like a baseball pitch counter, but it would rust.
I have a row counter sitting right here in my knitting supplies, but now I will have to wait until next year to use it, we just closed our pool this week. Thanks for the idea, I like to let my mind wander while I swim and I lose track of my laps constantly! Hmmm, maybe this could help me keep track of intervals on the treadmill too. . .