Disney has the only pool that has a separate infiltration system (part of the Mickey pool -- I think one of the ears) for babies in diapers. All the other lines post signs that kids in diapers can't use the pools.
True, you have to pay an hourly fee on Disney for kids under 3 or those who aren't potty trained yet, to use the nursery. However, Disney, Carnival and NCL are the only lines taking kids under 3 years in any kind of group babysitting or programming. NCL and Carnival take kids two years and older in their youth program for free. All the other lines (RCI, Princess, etc) only take those 3 yrs. and older.
Luisa Frey Gaynor
Family Cruise Editor