CdM's final touchdown came on a seven-play procession that made it 28-20 with 1:30 left in the third period.
Irvine (2-4-1, 1-0-1) led, 6-0 and 13-7 and chose to kick a PAT with 4:06 left in the third quarter that left it behind, 21-20.
The Vaqueros had three fourth-quarter possessions, but managed only a 25-yard Tim Callian field goal with 4:59 remaining to allow CdM to escape with a hard-fought win.
A 60-yard punt by Reinhardt pinned Irvine at its own 13-yard line with 1:23 left and the defense failed to allow a first down to take over for one last play from victory formation.
CdM was, arguably, its own worst enemy, as the Sea Kings, ranked No. 4 in the CIF Southern Section Southern Division, lost two fumbles, one of which was cashed in for an Irvine touchdown.
Irvine also benefited from a nine-yard punt that led to the fourth-quarter field goal. Irvine had a first-and-goal at the CdM four-yard line before settling for the field goal, after two runs lost four yards and a third-down pass fell incomplete.
CdM might not have had to sweat things out in the final minutes, had it held on to three would-be interceptions that were dropped.
The Sea Kings were also aided by a pair of long kickoff returns by junior Cole Cottrell. Cottrell took the second-half kickoff at his own goal line and sprinted 44 yards to set up his team's third touchdown. It was a 39-yard kickoff return by Cottrell that helped lead to a 60-yard touchdown drive that finalized the Sea Kings' scoring.