Apple

Ultra is designed for swim diving. I'd be wary if you are talking about diving off a cliff or such. That's a lot of impact force. Either way I'd not go in salt water with a standard Apple Watch. Only the Ultra and Ultra 2 are meant for that. And be sure to rinse them well after coming out of the water. I swam a lot with my Ultra in Bermuda this spring. No problems. Only thing I will say is the bands that come with the Ultra are garbage. They do not buckle up secure enough. Had the "Ocean" band fall off several times before going back to my old Nike Sport band. It's much more secure for me with the tail end of the strap going under the band holding the strap on the pin buckle. I won't trust any other band style for swimming except for the velcro style.