Re:
I have 2, use them for all training bar swimming in pools
#1 is an older Polar Accurex NV+ - from 1995! Still going, has had 3 batteries in the watch, and on 3rd strap unit (Battery is not replaceable). Can be downloaded if the PC you have still has a 9 pin interface... Very good for read back for up to 10 files and 16+ hours when reading every 15secs (Can be varied between 5 and 30) and setting zones and audible zone alarm. At last service Polar was unable to find a seal for it worldwide, so is now water/sweat protected by use of clear bath sealant... Love it. Simple, easy to use yet functions I've not used in 20 years. Was expensive at the time, has paid me back.
#2 is a newer Timex model, has similar features, but can only record one file at a time. Also gives calorific burn, which is handy. I now use this one for triathlons as the Polar isn't hugely water proof any more... Was under £100.
Also had a ££25 Decathlon one some years back - it lasted about 3 or 4 years, the strap broke and is not replaceable - moulded in one peiece... Did the basics - HR zones / alarms / calories burnt, Was good while it lasted.
At 50+ I use these and HR zones as well as feel when training and pace myself accordingly.