A honeymoon cruise to the Caribbean sounds great to me! The weather SHOULD be OK in July. As a rule the early part of the year is best, and once you get past June the weather starts to go downhill, until it hits its peak nastiness around the end of September. Then it starts to improve again. Don't get too obsessed with the weather though. Be very careful which cruise line you choose. Which destinations it visits, and where you have to fly to and from at the beginning and end of it, and with which airline.
A caribbean cruise is traditionally taken in the winter when the weather is bad in Europe. Consequently there is not so much choice in July as there would be in the winter months. Have you considered a Med cruise instead? A nice cruise to Venice, Dubrovnik and Corfu would be VERY romantic, and the weather should be great there. On top of that, you could sail direct from the UK if you wished, which would do away with that 10 hour return flight and any associated delays. On top of that, there is no baggage allowence to worry about! Since you have never cruised before I think this is something worth considering. Also, don't forget that the school holidays start in July, and most ships will be filled with kids at this time! If you want to get away from that, then P&O have a couple of child free ships that you might want to take a look at?
I would not go on a cruise to the Caribbean in July as it is hurricane season, a med cruise would be lovely in July and is definitely a better option. Have a great honeymoon what ever you choose.
Both the ideas given below are good but if you are set on the Caribbean then go. Ships are not like hotels in that they can move and no company wants to risk a multi million dollar item so they avoid any hint of nastiness in the sky. It is hot and can be steamy there in July but it is still great.. As you're on honeymoon maybe you can increase the atmospherics ...regards ..Nei.
I think you may find that many of the major cruise lines do not cruise in the Caribbean in June. P&O for example begin their Caribbean season in October and it finishes at the end of March. This is because of the danger of hurricanes from April to November.
Personally I couldn't think of anything more romantic than a Med cruise which takes in Venice. Imagine sailing into Venice on a sunny morning. Wonderful.