Hi sea Lotus,
Calling for help from a watch while at sea.... good luck with that ! I had to call from my phone once and it was already quite a struggle !
Any gps watch will do for your speeds, but I'd recommend taking a real phone with you, and not one with a touch screen.
The watch's speaker and microphone will be full of water and you'll have a hard time hearing and being heard.
I carry this sort of phone with me all the time . (has a flash light too

)
100$ phone on a 10$ plan, I value my life a little more than that