Iolo: Deifio yn y Barrier Reef Main cast, played by Iolo Williams Episode 1x01: Pennod 1 (Jan 4, 2018) Episode 1x02: Pennod 2 (Jan 11, 2018) Episode 1x03: Pennod 3 (Jan 18, 2018) Episode 1x04: Pennod 4 (Jan 25, 2018)