not sure if the GPS enabled starting devices are legal for buoy racing...

I use a $4.00 (USD) digital kitchen timer in a waterproof bag strapped to the boom.

It's annoyingly loud, has a huge display (digits are perhaps 1.5 inches tall) although doesn't give the 10-second beep countdown that the $100 USD Ronstan watch does...And it doesn't have a "Sync" feature, but you can't beat the price...

Given how many expensive devices I've donated to the fishes, if I lose this kitchen timer I don't think I'll have to re-finance the house to replace it.

I'm thinking I may "upgrade" to the old school wind-up egg timer (with the bell). Since it's mechanical, it probably doesn't even need to be waterproof. And everyone on the start line will know when my toast is done