Authorities in Orlando are searching for a two-year-old boy who was dragged into the water by an alligator near Disney's upscale Grand Floridian Resort & Spa.

Orange County sheriff Jerry Demings said a family of five from Nebraska was on holiday and wading in a lake on Tuesday evening despite "no swimming signs" when the attack happened.

"As a father, as a grandfather, we're going to hope for the best in these circumstances," Mr Demings said at a press conference.

"But based on my 35 years of law enforcement experience, we know we have some challenges ahead of us."