At the pier there are Taxis that will take you to 7 Mile. Many are vans that carry 15/20 people and charge about $6 pp. They are also waiting to take you back for another $6 pp. This is a very easy thing to do. Just make sure to allow lots of extra time for the return. Some time Grand Cayman traffic can take a while.
61 Carnival: Mardi Gras, Ecstasy X2, Fascination X6, Celebration, Elation X5, Glory X5, Fantasy X4, Valor, Holiday X3, Imagination, Liberty, Spirit X2, Freedom X3, Destiny X2, Splendor X2, Dream X2, Conquest, Legend X3, Victory, Sensation, Paradise, Inspiration, Magic X3, Triumph X2, Miracle X2, Breeze, Sunshine X3, Pride
7 Norwegian: Sky, Jewel, Dawn, Epic, Pearl, Breakaway, Getaway
8 Windjammer: S/V Legacy X3, S/V Polynesia, S/V Caledonia, S/V Diamant, S/V Sagitta X2