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.
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South and east Wales will stay dry tonight, there will be clear spells and very little wind but mist developing in the valleys.
Black History Month celebrations are continuing with a showcase of youth talent at the Wales Millennium Centre.
Bright and sunny spells throughout the day. Highs of 16°C.