Kite surfer here, we use them to control go pros (which are out of reach, say up in your lines or on the kite) also for data read outs from Woo sensor (a trick and jump height monitor)
I bet other water sports are using these watches in similar ways. E.g. GPS
Yeah but you're not sitting out on the break babbling on about work or doing selfie video calls to your partner. That's annoying enough on public transport, in the surf it would ... well it would make stand-up paddle boarders seem cool by comparison.