Do you plan on getting laser treatments soon after your cruise? If so, stay with the SPF 30. Bullfrog is supposed to be a good brand. Banana Boat is good also. Be sure to reapply frequently and apply it generously. Buy your sunscreen in the US as they will price gouge you in the Bahamas and on the ship if you buy it there.
Sun worshipper that I am, I can’t believe I’m telling someone to use SPF30 LOL! But if you’re going to have laser hair removal you need to avoid tanning. You can always hit the casino on the ship.
I don’t get laser treatments in the summer as they would interfere with my tanning. All my chest hair is gone as is most of my back hair so that’s OK. I can still have electrolysis there and still sun worship.
Enjoy your trip and respect the sun. It is a lot more intense in the Bahamas than in the Midwest or Northeast USA. Even I use higher SPF sunscreens when I go to the Bahamas, especially in the spring. In the fall the sun is not as intense.