I have to say that they look legitimate - but I personally would not put my passport number into any form along with all of that personal information. It is just too much to give away. Simply having all of that information about you and thousands of other people is enough to sell the list for thousands of dollars.
I would suggest calling them first and asking for THEIR references - and ask them what they get out of placing you on a cruise line.
I do recognize the list of "client companies" they claim to have - and they are real companies. But I also know there is no reason you cannot contact those companies - or most cruise lines, directly anyway.
I don't know if it is a scam - but I see nothing that truly convinces me they will help you get a cruise ship job,