“ 275 pounds is too heavy to be safe on a job-site in the North Sea.”
I’ve worked rigs on the North Sea and am over 275. Mind you, I am almost 7 feet tall. My waist is 33” and am in the low teens of body fat.
You just sign a waiver saying “you know you’re screwed”, take the training for the boats and move on with life.
As I said, in my other reply, it's not you that concerns me, it's the physical limits of those who would try to save you in a dangerous situation put at risk because of your size. It's not about the fitness of the individual; it is about the safety of the team.