A man has been arrested on suspicion of murder after a woman in her late 80s was found dead at her home by members of her family.
The pensioner's body was discovered at the address in Atlantic Close, Ocean Village, Southampton, on Saturday night.
Her family had not heard from her since Thursday.
Police said the arrest of the 37-year-old local man was part of only one of several lines of inquiry.
The area around the unnamed woman's home has been searched and officers have appealed to possible witnesses from the boating community to come forward.
A post-mortem examination is yet to take place and formal identification is still to be confirmed as some close relatives have still to be notified, a Hampshire Police spokesman said.
Detective Superintendent Rachel Farrell, who is leading the investigation, said: "I would like to reassure residents and those who visit this area that this is an extremely rare incident."
She added: "Due to the waterfront location of the address, we would extend our appeal to the transient boating and sailing community who may have attended the Cowes Week celebrations on Friday or sailed into or out of Ocean Village during the weekend.
"They may have seen something, no matter how insignificant it might appear to be, that will assist us.
"We have a dedicated team of more than 60 police officers involved in the investigation who are conducting searches, completing house-to-house enquiries and following up other lines of inquiry."
Police are appealing for people to contact them if they saw anything unusual or suspicious in the area of Ocean Way, Pacific Close and Atlantic Close any time between Thursday, August 16, when contact was last made with the woman, and the early evening of Saturday.
Ocean Village's website describes it as a large, mixed-use marina, residential, business and leisure development on the mouth of the River Itchen
:: Anyone with information can contact police on 101 or Crimestoppers on 0800 555 111.