To seriously answer your question, you will see more speedos on a Mediterranean cruise since there will be a higher percentage of Europeans on board. Wear whatever you are comfortable with as I do (always speedos). On my two recent Caribbean cruises, there were men in speedos in the pool areas although more with Costa than with Royal Caribbean. Although some men would look terrible in speedos, they probably wouldn't look any better in board shorts...a huge belly will hang over the waist in both! So do what you want to do and quit worrying about what other may think. Chances are if you are a competitive swimmer and have that swimmers build, the women will like what they see.