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This may help but you need to pick a cruise you fancy then contact the cruise company and they will tell you what they will accept as they view the cylinders as a potential risk? my nephew had to get a letter from his doctor to say he was fit to travel and needed the oxygen,they do not supply the oxygen except as a medical emergency and that cost? they will require you to have travel insurance,and booking a cruise from a UK port may be better, But book one and enjoy?
I know that you are able to take liquid oxygen onboard P&O, however they will request a full specification on what the oxygen in carried in before you travel.