PC Nathan Lucy swam out after the woman, who'd jumped into the water from the Red Jet terminal.
Review Published Into Weymouth Mum's Murder By Son
The authorities missed opportunities to act before a Dorset teenager obsessed by knives killed his mother by stabbing her 94 times, an inquiry has found.
Kieren Smith, then aged 16, knifed his mother Leah Whittle, 42, repeatedly at their home in Weymouth in July 2012.
Winchester Crown Court heard that Smith, who had been expelled from school at the age of 14, had spent the previous two years alone in his room, watching DVDs.
The eight-day trial heard that Smith attacked his mother in the flat they shared before he lied to police, saying she had been killed by drug-dealers.
Smith was sentenced to a minimum of 15 years' detention after being convicted of the murder by a jury.
Following Ms Whittle's death an inquiry was commissioned by the Dorset Community Safety Partnership to establish what lessons could be learnt.
The report concluded:
"This is an extremely tragic case for all concerned and it is important that all possible steps are taken to learn lessons and improve practice in the future.
"The overarching conclusion must be that it would have been impossible to predict accurately that A was at risk of being murdered by B, and that practitioners generally acted in good faith within their current knowledge base and work environment.
"However, there were lost opportunities to act differently and lessons that can be learnt which should improve the response to similar situations in the future.''
Since the review began, agencies across the county including Dorset Police, local healthcare organisations and Dorset County Council have all made changes to their services to try and minimise the chance of such a tragic case happening again.
Councillor Ray Nottage, chairman of the Dorset Community Safety Partnership, said:
"This was a very tragic case and I'd like to express our condolences to the family.
"The review, which examines the circumstances of this case and agencies' involvement with the family, allows us to look at how organisations work with families and highlight where lessons can be learned - in particular, improving agency knowledge of, and response to, parental abuse.
"We want to create safer communities, so it is vital that victims of domestic violence, their friends, family and the wider community report abuse to the police or some other local agency.''
As Smith was under 18 the review also considered the involvement of children's services, as well as those working with the mother.
Cliff Turner, chairman of Dorset's Safeguarding Children Board, said:
"Although there were many agencies and services working with both the mother and son, it appears that there was not one particular service or agency that looked at the whole picture.
"Since this devastating case, agencies have been working very hard to address the areas highlighted in the review and change the way they operate to make sure the right information is shared with the right people, at the right time, to reduce the risk of a similar case happening again.''
Dorset County Council has already made changes to its social care assessments and has trained staff to deal with more complex family situations.
The council has also made sure that young people who are not going to school regularly, and who are not being seen by a professional, are subject to a multi-agency planning meeting to assess their whole situation.
Councillor Rebecca Knox, the cabinet member for children's safeguarding and families, said:
"This was a terrible case that was extremely distressing for the family involved.
"Although such cases are very rare, it has made us review how we support families, particularly with teenagers, find new ways to work with those that are harder to reach and improve the way we respond to the more complex cases.
"We are committed to supporting children, young people and their families across Dorset, and are doing everything in our power to minimise the chance of such a tragic case happening again.''
Dad-of-two Nick Medlin from Ventnor died after being assaulted outside the Rose Inn pub in the town.
A section of Parkstone Road will be affected between 9.30am and 4.30pm for three days.
A man's died in hospital after a crash in Eastleigh.
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