Bad idea.
It isn't about looking good in a bikini. (I'm sure you're gorgeous)... It's that babies can and do regularly get born at 7months. And 8.
7 months is VERY viable, if and only if, you are near immediate medical attention.
Will everything probably be fine?
Yes. You will probably deliver at 9 mo ths with no complications.
But for the 10's of thousands who have preemies every year... Even half an hour is crucial... Much less the 1-4 hours it takes a plane to land (over land or sea) in event of a medical emergency, and days to reach a hospital while on a cruise.
At 6 months, your baby would probably die, anyway. Which is harsh and brutal, but true. At 6 months some babies survive, but most don't. At 6 months, it's generally 'okay' to travel, because the options are essentially the same.
It's a rule of thumb with me: whenever one of the probabilities is my son's death, I go out of my way to avoid it. Car seats. No running near cliffs. That sort of thing. Which includes staying near medical attention / facilities when in my last trimester and he's viable IF I can get immediate medical attention.