Keeping time : When Your Pool Doesn't Have a Clock
It is possible that you will be swimming at a pool that does not have a clock. If that is the case, there are a few options:
Watches
There are a number of watches on the market for both swimmers and triathletes that will work in lieu of a clock at the pool. I am not a big fan of wearing a watch in the pool (though for triathlons I definitely do), just because when I get to doing intervals on tighter bases it can sometimes be a pain to hit the wall, orient yourself enough to look at the watch, register what it says (or get the face to wake up, in the case of Apple), and push off the wall in time. However, if you are doing a timed swim, having a watch on your wrist that can vibrate to let you know when you've hit certain times is a great help.
I personally have used the Garmin Forerunner 225, Apple Watch Series 2, and Timex Ironman Watch (all included on list below, I did a blog post on using each of these here).
In addition to those, below are a few options for watches that have received decent reviews:
Apple Watch (Series 2, but Series 3 also has swim capabilities)
Garmin Swim - keep in mind, Garmin makes a series of watches for multisport athletes, this is just for swimming, so if you are a triathlete I'd recommend doing more research on other Garmins.
Clocks
I spent a decent amount of time online trying to find a small deck clock that you could carry in your bag and put at the end of your lane, and at this point I swear they don't exist. Enter: shower clocks! Amazon has a huge variety of them in both digital and analog in a number of sizes. Sticking one of these at the end of your lane during a workout may be the next best option to a wall-mounted clock.
Lap Counters
A lot of swimmers like lap counters. These are small devices that fit over one finger and allow you to to click a button with one hand each time you turn.
Some lap counters include timers, others don't. SportCount seems to be the only company that makes waterproof handheld lap counters for swimmers (if you find another, please let me know.)
If this doesn't work for you, you can always just keep a stack of poker chips at the end of the lane and use that to count our laps like my Uncle Joe does.