Welcome aboard, Gaspar! It sounds like you've visited the parks at Walt Disney World before, and you're ready to experience life on the high seas with Captain Mickey now!
Disney Cruise Line does not currently use MagicBands for guests aboard the ships. What you saw was a Disney Cruise Line Youth Activities Wristband, which looks very similar to the Walt Disney World MagicBands. These Youth Wristbands are worn by children to get access to the
Oceaneer Club and
Oceaneer Lab onboard the ships and to Scuttle's Cove at Castaway Cay. They simply tap the band to the reader, just as a guest would at Walt Disney World, and the Cast Member checking them in then has their information, so they know which children are in the club at that time. Children receive the bands when the family checks into the Youth Activities desk at the port terminal or onboard the ship.
These bands are complimentary for use on the ship, and must be returned at the end of the sailing. Guests can, however, choose to purchase the band as a souvenir at the end of their cruise, should they desire to keep it. The last time I sailed, it was about $13 to keep the band.
Instead of MagicBands, Disney Cruise Line uses Key To The World Cards for guests as their onboard account card. It is the key to their stateroom, charge card for purchases onboard, identification, and contains information on the front about their dining rotation. Guests often choose to wear a lanyard so that they can slip the Key To The World Card in a pouch on the front and have it with them without having to carry an extra bag.
I hope those details help as you get ready to set sail, Gaspar! Let us know if you have other questions before you head out to sea with Captain Mickey and his crew!
Marcy