I use your basic Timex sports watch, water proof to 100 meters which means you never have to worry about getting it wet. They have timers but I find that most Race Committees generally have the correct time so keep yours on the correct time and you should be able to help him out. Many skippers prefer to rely on crew for a time count down, say every 30 second until the last 2 minutes then every 15 seconds after that. they have a lot to think about just before the start so an automated time to go reference is very appreciated.
If you goggle Standard time it will lead you to a US government sponsored time display that is very accurate.