I have several Suunto watches, sadly the countdown timers do not loop.
The race timer on Ronstan and Optimum Time races watches do, but they beep on every minute and go crazy on the last. Not exactly ideal.
Mine does; the Suunto M3-- but there may be more beeps in each cycle than are wished for.
2. USING RACE TIMER
The Suunto M3 helps you to optimize the timing for the race start so that you can
cross the start line at the right time. This helps you get ahead of your opponents and
avoid turbulence from the other boats in front of you.
The race timer helps you to follow the official race start countdown.
1. Long press the MODE button to switch to the Timer view.
2. Press ENTER and select Start time.
3. Enter the countdown time with the UP/DOWN buttons. For example, if the official
signal is given 5 minutes before the start, enter 5.
4. At the official signal, press UP to start the countdown on the Suunto M3.
TIP: You can set the timer to repeat the countdown. This is useful if there are
several race starts, for example, for different boat classes.