Don't make the mistake of limiting the countdown options to whatever the rulebook currently says. I have an expensive watch that can only do 5- and 10-minute sequences. I sail at a club that uses 3- and 6-minute sequences for some events.

I think the old-style Timex Ironman was a nearly perfect sailing watch, with buttons on the face rather than the sides where they could accidently get pressed when tacking. I have three of them, got them all for under $20, and have replaced batteries several times.