A man has been arrested on suspicion of manslaughter after another man fell from a boat off the Dorset coast.
A search involving the RNLI, HM Coastguard, police and Dorset Search and Rescue is under way for Mr Haw, from Sussex.
Dorset Police said a 19-year-old man from the Southampton area has been arrested on suspicion of manslaughter and remains in police custody.
Detective Inspector Wayne Seymour said: “Our multi-agency search efforts are ongoing to locate David and there will continue to be a police presence in the harbour and surrounding areas.
“We are continuing to keep David’s family updated with any developments and are doing all we can to support them at this difficult time.
“We are carrying out enquiries to establish what happened in order to help us locate David and would urge anyone with information that may assist our searches to please get in touch urgently.”
Mr Haw is described as white, 5ft 10in inches tall, of slim build, with short mousey brown hair. He also has a short beard and bushy eyebrows.