Steven Johnson, 61, was last seen at around 7.30pm last Tuesday, 4th December, when he returned to his houseboat after having dinner with a neighbour at the marina.
Police are making enquiries with residents in the vicinity and searching the surrounding area.
The underwater search team is scouring the marina waters and the wider Chesterfield Canal in search of Mr Johnson.
They will also be trawling the depths using special sonar equipment.
Mr Johnson is white, of slim build and 5ft 8ins tall. He was wearing sandy-coloured rigger boots and a dark-coloured jumper and trousers.
“We are supporting Mr Johnson’s family at this worrying time,” said Det Insp Ash Wilson.
“They are understandably very anxious, as it is unlike him to leave without letting them know where he is going.”
“He also never goes anywhere without his lurcher dog Dabber, who is being cared for by a friend in her master’s absence.”
“We are very concerned for the welfare of Mr Johnson. He had been feeling unwell in the days leading up to his disappearance.”
“That, combined with the freezing temperatures, means it is imperative that we locate him.”
“If you have seen him or know of his whereabouts, please call us immediately.”
Anyone with any information should contact Notts Police on 101 or Crimestoppers anonymously on 0800 555 111.