Searches have been continuing on the sightseeing boat at the centre of the investigation into the death of a teenager and child in Bournemouth.
The boat was impounded by police after Wednesday's incident, where a 12-year-old girl, named locally as Sunnah Khan, from Buckinghamshire, and a 17-year-old boy from Southampton were pulled from the sea.
Another eight people were treated by paramedics.
On Friday, the Dorset Belle remained guarded by a police van at Cobb's Quay in Poole Harbour.
A man in his 40s - who was "on the water" at the time - was arrested on suspicion of manslaughter and released under investigation on Thursday.
According to the website Marine Traffic, the boat had visited Bournemouth Pier, the scene of the incident, at 4pm, minutes before the first 999 calls were made, and returned afterwards.
Police said no physical contact was made between the swimmers and any vessel or jet ski, and that those involved had not been jumping off the pier.
Bournemouth, Christchurch and Poole Council (BCP) said it hadn't licensed the boat and that the Maritime and Coastguard Agency (MCA) was responsible for issuing licences to vessels the size of the Dorset Belle.
Police declined to comment on any investigation into the boat and refused to say if any vessel was involved.
Tobias Ellwood, Conservative MP for Bournemouth East, said he believed police should provide more information to avoid "wild speculation".
He added: "The police are conducting their investigation, there needs to be a review of the circumstances to see whether any safety measures and protocols need to be upgraded to ensure this doesn't happen in the future.”
The boat's website states that it was purpose-built as a passenger vessel to operate locally and could "cope with the occasional challenging swell conditions encountered at local piers".
The council's website says that, from April to October, yellow buoys are set out 200m from the low water mark to indicate that watercraft must not "go beyond six knots, annoy or endanger other beach users or run ashore or launch from the beach".
Councillor Vicky Slade said: "There is no evidence to suggest any of those rules have been breached.
"We are confident with our partners that any lessons that need to be learned in the future will be learned."
Dorset Police are working with the Marine Accident Investigation Branch and the Maritime and Coastguard Agency to investigate the incident.