We did a caribbean cruise a couple of years ago and didn't have any jabs before we went. During the day all we wore was swimwear, short and t-shirts. In the evenings on the ship, my OH wore trousers and shirt and I wore a nice dress or skirt and top. Depending which ship you are going on, some of them have formal nights in the dining room, where the men are expected to wear a tuxedo but we didn't bother - on those nights we just went upstairs to the buffet.

no you do not need any specific vacs but would advice making sure you are up to date with tetanus,polio,hep a and typhoid which are the usual holiday jabs for turkey and beyond.we did not get bitten once in 15 days but as you are usually sailing in the evening the risk is slight but I would still advise some deet spray as a precaution.dress wise shorts and teeshirts in the day,smart slacks or skirt and tops for casual evenings and I usaually take 2 evening skirts or trousers and 4 sparkly tops for formal nights.men need an evening suit plus smart slacks and shirts.we have cruised with variou s companies including thomsons but only p&o in the carribean but im sure it will be similar.have a great cruise,it wont be your only one im sure