Become crew on a ocean-crossing yacht.
There are a number of agencies that will hook you up with a yacht making transatlantic crossings. Some of these (yachts) will charge you for the experience, in other cases, skippers simply needing crew to fill spaces on watches will take anyone who know what a rope looks like and can prove they can swim.
I was > < close to going transatlantic on a nutty 26ft yacht with it's single-handed owner (Geoffrey Hales), he was sailing it over in the then-OSTAR race, I was joining him in NY and brining it back.
I went on a couple of training trips with him on that thing, it was way OTT for something 20 years ago. Twin rudders at the back, another at the front, massively oversize fractional rig. SMALL.
Completely silly. It broke it's boom 2 days out of Plymouth and that was the end of my Atlantic trip.
I had another chance to cruise the Baltic on a
65ft Swan but we collided with another yacht on a shakedown cruise in teh Channel Islands and that was off too.
Finally, I was in Canada when Geoff Hales entered a 30ft catamaran in the Round Britain race in 1996 or so. My Dad and brother went on it and told me about surfing waves downwind at 30knots.
I cried.