Here is what my Navigator from January 2, 2004 says.
"FOR THE HEALTH AND SAFETY OF OUR GUESTS, PARENTS MUST OBSERVE THE U.S. PUBLIC HEALTH SERVICE REQUIREMENTS BY ALLOWING ONLY CHILDREN WHO ARE TOILET TRAINED TO ENTER SHIPBOARD POOLS & SPAS. CHILDREN WHO ARE NOT TOILET TRAINED MAY USE THE FOUNTAIN PLAY AREA LOCATED IN MICKEY'S POOL STARBOARD EAR, SWIM DIAPERS ARE REQUIRED"
So untoilet trained kids can't go in the Mickey pool proper, the port ear, or the Goofy pool, but they can go in the starboard ear IF they wear swim diapers.