I would not say that it's safe, IIRC one ship per week is "gone without a trace". Maybe insurance fraud, maybe pirates, maybe the kraken... But it is much safer than other modes of transportation. What would bug me out on the fright ships, what does the smutje cook up? How to spend your time? Can you go for a walk on deck? One day I would like to try, but more research is needed.
My mate who did that trip said that was part of the attraction, you are forcibly removed from everything on land, there's no internet connection to the outside world, all they have is an emergency satellite phone, and it gives you a complete break from everything back home. Once you're under way, you know there's no way off the boat for the next 6 weeks or however long the voyage is. And you get to learn about the sea, see all it's different moods, and wildlife. And you eat with the crew and other passangers, swap stories, have a completely different experience. It's an adventure that takes you out of yourself.
He said they let him onto the bridge and showed him the rudiments of how the ship works. He said the food was great, they eat very well, it's probably good for the crew's morale. Of course you have to "muck in" with everyone else. I'd like to do it myself some time, but the time to go is when you're young, really. There's usually no doctor on board, that is the reason the number of passangers is restricted; one of those videos I posted said that regulations only allow them to take a maximum of 12 passengers on a ship with no doctor, so there aren't many berths on each boat. I think my friend said there were only 5 passenger berths on his boat. Of course you need to be sensible, you know your own health. You're going to have a hard time if you need to be airlifted off the boat in the middle of the pacific, if that's even possible. I think it's really a trip for someone young and adventurous who wants to see a bit of the world, or at least young-at heart and adventurous!
I guess being in that space capsule going out past the moon is an extreme version of the same thing! They all look pretty happy in the videos of them being interviewed while they're out there, I am full of admiration for them.
Yeah, you might not want to take a route that passes up the coast of Somalia, or other areas where there are pirates. As for krakens... well, who knows!??