My husaband was celebrating a special birthday on ship and a freind E mailed him, but to receive the E mail we had to pay at reception to receive it also they had sent a picture with it which did not arrive.
Pictures are blocked - for obvious reasons !!! think about it.
The Ocean Village ships have a cyber cafe and emails can be checked there for a small charge, but they may not want to do this whilst on holiday, but if for a member of staff possibly the best way if you know their email address. The other option is to send a fax to the ship contact there UK base and they will give you the fax number, so long as you have access to a fax. If the person is with a partner you could give them a card to be handed over on the day in question. Another option is a text message but they need to have their mobile switched on to receive this and not sure if OV is equipped with the system most ships are now having installed to allow to use your mobile even when at sea. We were down in New Zealand earlier this year and I used text very successfully, the signal was as good on the ship as it was onshore. What ever you do don't use the telephone or mobile to contact them as it is not very cheap and it will be them who will be picking up the cost.
E mail will work if they subscribe to the internet on board - if not fax them from the Post Office/ local shop/ Library/friends office etc. You can also phone them for £3pm if you know their cabin number ! Mobiles WILL work as the ship is fully up to date BUT it depends on whether your friends Sim card/network will allow the phone to make/accept calls via a satellite mobile link. Many dont as I found to my cost (and I had 2 different sims/networks) !!
You dont state whether or not they are already on the cruise. If the cruise is not yet departed, why not send a B/Day card to the cruise co Offices, clearly marked with persons name and cabin number, well in advance and they should then forward this on.