Four sunken boats in Rhyl's harbour are to be moved because they are considered a risk to other vessels.
Vessels in harbour at high tide have to navigate four submerged wrecks
Denbighshire Council says the wrecks in Foryd Harbour are a danger because they are submerged at high tide.
The local authority wants the vessels, one little more than a keel stuck on the harbour floor, to be moved as part of a £1.4m revamp of the waterfront.
It said people claiming the private boats would need to provide proof of their ownership.
The council said it had been unable to find the vessels' owners, three of which had appeared in the harbour in the past six months.
Paul Smith, the council officer overseeing the regeneration project, said the local yachting and fishermen's organisations had collaborated with the search, providing lists of their members and the vessels they owned.
He said: "A lot of the moorings we know something about. It's the ones we don't know about that are the problem."
One of the wrecks (marked) in Foryd Harbour
The council has given the owners of the four vessels until the end of the month to claim their boats or face seeing them removed.
It is taking out adverts in local newspapers and putting notices at the harbour and in council offices.
Mr Smith said the boats were a "navigation difficulty" for other craft using the harbour.
He said: "They all sink when the tide comes in. If you don't know where they are, and the tide's in, you will hit them.
"It's a danger to shipping. It means that boats can't easily move about the harbour and no harbour wants that."
He said the vessels included a single-masted yacht called Shelldrake and a blue boat known locally as The Lowri.
The remains of another two vessels, by the harbour wall, the City of Ottawa and the Alice, will not be removed as both are considered to be historically important.
The first phase of the harbour's revamp started in January.
The work will see a new road constructed from in front of the May Quay public house to the former timber yard, repairs to the timber yard quay wall, the creation of a secure boat storage area with wash-down facilities and a new cycle route link.