Police say neither of the two men involved in a fatal boating accident on the Kapiti Coast were wearing lifejackets.

One man is dead, and the other missing after their inflatable boat capsized near the Otaki River mouth yesterday.

A full-scale search is underway today for the missing man.

Sergeant Bill Nicholson, who is coordinating the search today, said there were about 18 people involved in the search, including police, landSAR, air patrol, and members of the public.

The search stretches from Waikawa Beach to Paraparaumu, but the forecast has led searchers to believe if the man was to be found, it would be just south of the rivermouth.

He urged the public to keep an eye out if they were on or near the water for the man, who is Caucasian, in his 30s, and wearing dark clothing.