The RNLI says the man and boy were were swept out to sea off Aberffraw, on the west coast of Anglesey.
The man was able to make his way back to shore, but the child is still missing.
More top news
The whole of Wales is covered by a yellow warning to be aware of very strong winds developing tonight.
Did you miss any of our coverage? Catch up here on Wales at Six.
Catherine Herridge made a remarkable discovery...