Yes they can. In the mickey pool, one ear is reserved for the toddlers on board. They must have swim diapers on and you must keep an eye on them, no life guards for that. The ear is only 2 inches deep, but it has several jets of water that shoots from the inside of the ear. The kids love it!! You can sit on the ear and put your feet in to make it easier to watch your child. Parents do this all the time. My grandson just loved that pool. The other ear is deeper and is for the kids who are older, but not big enough or confident enough to go into the regular part of the kids pool.
They do sell swim diapers on board, however they are spendy and they do seem to run out quickly. It's best to pack plenty when you come or buy them the first time the stores open up. The pool is in the direct sunlight, so bring plenty of sun block too.
Kathleen , 7 times DCL cruiser
We went on the Wonder April 2003 and my 2 yr old daughter was not potty trained and they told us while we were in the pool that she needed to be taken out of the pool with her swim diaper on. However we leave on Sept 11, 2005 on the same ship, will keep my eye open and let you know.