A kayaker in distresss who sparked a search on the Waikato River last night has called police to say he is alive.

Police said the man, last seen yelling for help while floating down the river in Hamilton, had ditched his kayak and swum to shore.

A rescue operation had been launched after police found a kayak and paddle.

A spokeswoman said the kayaker contacted police around 4am to advise them he was safe and well.