Especially the surface of the open ocean. There's little out there compared to near land. And even if you happened to pop near a shark feeding frenzy, for 30 seconds hold your breath, let yourself sink if that happens, and just don't move at all.
As written it's just five years 365 times. The odds are very good for survival. To make it more questionable, have the owed time be five years total in your life of 30 seconds accumulated. Still the same factors apply, 30 seconds isn't a life risk. Add in the choice of extending any of these to longer than 30 seconds before the pop to use up the time. Now survival becomes questionable if you gamble too much or at the wrong time.