As with any cruise be careful if you are doing tours on your own. In my 4 cruises we have seen 2 groups of people left at port as they were not back on time. If you go with a ship sponsered tour you will pay more but you will not be left behind and you are on a trip that is a "known".

I've done both on my own and paid threw the ship. To us its worth the extra $$$ just for the peace of mind.