Devon snatched victory with the last play of the game when Teignmouth full-back Aaron Smith scored a try and Ivybridge’s Mitch Pinkus calmly converted.
Earlier Exmouth flanker Max Keen had scored a hat-trick of tries for Devon, which were all brilliantly converted by county captain Pinkus.
Pinkus formed an all-Ivybridge half-back pairing with Jay Toogood, while club colleague’s Wes Vermingle, Ben Collins and Marcus Prout lined up in the front-row, with Owen Garner on the bench.
Services’ Swatton was making his Under-20 County Championship debut. He started in the centre, alongside Brixham regular Jesse Lowe.
Devon finished their group games unbeaten, having drawn 10-10 away at Somerset in their opening match. They are now waiting to see who they will play in the quarter-finals.