Someone who has no experience in a boat, who is also on a boat they are unfamiliar with, is probably also not that familiar with navigation.

And over the horizon can easily be outside of cell phone range. And is definitely outside of visual range.

So it seems prudent to do a ‘don’t get yourself killed, seriously.’ Warning eh?

5km out to sea is far more dangerous than you think. For starters, you're 5km away from help. The water is deeper, and the currents and wind stronger.