Police said that their destination was not known but they were headed in the direction of Stranraer.
A search for two men, missing in their speedboat off the coast of Dumfries and Galloway since Saturday, has been called off, Police Scotland has said.
The alarm was raised at 4.15pm on Saturday when the pair failed to return to Port Logan.
Two helicopters, coastguard rescue teams and several lifeboats are involved in the operation to find the men, who are aged 46 and 35.
About 10 rescue teams were involved in the search, which resumed on Sunday.
The bodies had yet to be formally identified but police believed they were the missing men.
"Inquiries are ongoing to determine the circumstances surrounding the incident".
The painstaking search - covering a meticulously planned area based on the vessel's known and projected movements - continued through the night but nothing has been found.
Earlier Maurice Neill of RNLI Donaghadee said: "The water temperature is still very cold at this time of year, it's only 10C or 11C and your chances of surviving in the water for much longer than an hour are very poor".
A coastguard spokeswoman described the search as "extensive" and said: "Portpatrick, Stranraer, Ballantrae, Isle of Whithorn and Bangor Coastguard rescue teams were involved, along with lifeboats from Port William, Stranraer, Donaghadee, Ramsey and Peel".
It is not known how many people were on the speedboat.
Lifeboats were also launched from Port William and Stranraer as well as other crews from Northern Ireland and the Isle of Man.