Regardless if the time of year you visit, your snorkeling time will be much more comfortable if you have a wetsuit. I would recommend a full 3 mm suit if you have one available but any suit that fits you is better than none. Many – but not all – of the yachts and ships have wetsuits available on board. Some include this in the cost of your cruise while others charge an additional fee. In any case there will be a limited number of suits in each size so if you have your own wet suit, I would recommend that you bring it. If you are unsure if the yacht/ship you will be on has wetsuits available – ask.