Hi, I was thinking on buying a Coros Apex 2 pro watch for speedwindsurfing, but noticed Coros downgraded the water rating from the previous Apex Pro from 10 to 5 ATM on the current Apex 2 Pro.... everywhere I have checked states 5 ATM rating is not safe for watersports, and recommend at least 10 ATM... so the only option would be the Vertex 2, which is older, a lot more expensive and an overkill just for windsurfing. Guess I'm staying with my GT31 for now and hope Coros next Apex watch is 10 ATM again. 
 

If you have any question about the specifications of Coros devices please contact Coros directly for this at -> 

https://support.coros.com/hc/en-us