I tend to agree. I usually claim that I can't swim, as what I do doesn't really constitute swimming, but I can stay afloat and move in a deliberate direction.

A complicating factor: Swells and bad weather make it a lot harder. But on the flipside, no matter how badly it goes, if I'm teleported back in 30s I'd just fill my lungs beforehand. I can hold my breath for much longer than that, and even if I couldn't, it would take more than 30s to die from oxygen deprivation - just make sure I have EMTs on standby for when I return.