Thomas Courto, 26, left Wynyard with friends Isaiah Dixon and Bree-Anna Thomas on October 18 in a five-metre yellow-and-white motorboat.

The bodies of Mr Dixon and Ms Thomas were found washed ashore near Table Cape two days later.

A two-day sonar survey was conducted earlier this week after aerial, sea and land searches failed to find any trace of Mr Courto or the boat.

Tasmania Police said analysis of the survey identified an "area of anomaly" on the seabed near the coastline.

"Police divers will search the area identified," they said in a statement on Thursday.

Earlier search efforts for the trio, who all lived in the northwest, were hampered by rough seas and strong winds.

Mr Dixon's uncle has thanked the tight-knit coastal community for their support, describing his nephew as having a beautiful heart.

Vigils have been held at the Wynyard boat ramp and flowers and messages have been left in a local park.

The group was reported missing on the afternoon of October 18 when they failed to return.

Australian Associated Press