It seems as if some water got inside the device, which shouldn't happen to being with. I'd suggest that you get in touch with customer support.
Regardless of the outcome, I'd also recommend that you put the thing in a bowl of dry rice for about 24 hours or so. If there's any moisture causing the watch to act like that, removing it may help get it back to normal. Even if this works, however, the whole situation means that you cannot get the Versa wet, which is counterproductive.
Thanks for your reply, your tips were very useful. It's stopped vibrating after drying out. I contacted customer services and they suggested shutting it down and restarting. They also asked if I was using a 3rd party clock face. No sure why that would be a problem! Waiting for their reply. Swimming tonight so will see if there is still an issue. Concerned as it will be a year old on the 22nd!
Best AnswerAfter your swim tonight, if it does it again I would take a video of it happening and then open up a case with support. They are really good and making things right. So make sure you beat that 1 year deadline.