Prince Charles visited Stebonheath Primary School, Llanelli, where he was shown a water catchment system and was treated to a concert.
He later met the youth team at Llandovery Rugby Club, Carmarthenshire, of which he is a patron.
The prince also visited Aberdare's Prysmian Cables & Systems in Rhondda Cynon Taff.
And he was given a tour of parachute manufacturer Airborne Systems in Llangeinor, Bridgend county, where he met staff and apprentices.
The Prince of Wales spent the day meeting young people in Carmarthenshire during a visit in the region.