Police found Daniel's fishing gear on the pontoon
Police in Hampshire fear Daniel Nolan, 14, may have fallen into the chilly waters of the River Hamble near his home in Hamble, Hampshire.
The boy was reported missing by his parents in the early hours of Wednesday when he failed to return home.
He had been fishing with friends on Tuesday night but was not seen after 2330 GMT.
Strong currents
His fishing tackle and gloves were found on a pontoon by the river.
The temperature of the water would have been 5C and a police source said that if he had fallen in he could have survived for only minutes.
There are strong currents in the river which flows into the Solent.
Police, a coastguard helicopter, lifeboats and a Royal Navy diving team spent Wednesday searching for Daniel.
But failing light and a high tide made searching difficult.
Police said Daniel visited the river three times a week and had his own boat and was very experienced by the water.
Too cold
A Hampshire police spokeswoman said: "We are still hopeful but at this stage there is a strong possibility he has fallen in the water."
Daniel, who was wearing a red fleece jacket, had been fishing with three friends on a pontoon at Hamble Marina.
Walking back he bumped into his friends who said it was too cold to fish and were going home.
Daniel said he would return to the pontoon to retrieve his fishing tackle and meet them.
The teenager, who has three brothers and a sister, has not been seen since.
He was expected home by 0200 GMT on Wednesday.
Inspector Paul Briggs, who is leading the search, said: "We have searched every possible location between the pontoon and his home and the shop we know he visited and we have found no sign of Daniel.
"We will not give up hope and we will continue to search."