The 18-month-old boy, found in an upper-floor fountain at about 1:30 p.m., was not breathing and had to be revived with CPR by police.
The boy remained hospitalized today with life-threatening injuries, police spokesman Officer Albie Esparza said.
Esparza said the family had gone inside the hotel to take pictures when the boy disappeared. Minutes later, he was found in the fountain.
Investigators are reviewing security video footage at the hotel to make sure there was no foul play involved, but he said the case appears to have been simply "a tragic accident," Esparza said.