Riding the momentum of a four-match winning run, the Seagulls looked set to add another victory to their tally at three-quarter-time at Box Hill City Oval.
While Williamstown’s advantage was just 10 points, it kicked the last four goals of the third term to assert its authority on the contest.
But the reigning premier found another gear in the wet in the final quarter, booting six majors to one for a 14.9 (93) to 10.12 (72) victory.
“Really disappointed with a couple of mistakes we made in that last quarter,” Collins said of his message to his players.
“We gave the first two goals away through silly errors in regards to defensive third man up, where they should have stayed down and (Box Hill’s) men stayed down.
“They had huge spaces out the back and that’s something we need to cover off, so that was poor by us as a coaching group.
“But the third message was that we lost it in the first quarter, not the last quarter.”
The Seagulls lacked polish in the forward half during the opening half-hour, converting just one goal from six scores and trailing by 15 points at the first break.
The visitors cut the deficit to just nine points at the main break, with the top-four contenders treating the crowd to an enthralling battle.
Williamstown’s Anthony Anastasio threaded a remarkable goal from the boundary just before the half-time siren to give his side’s supporters reason to cheer.
With the rain beginning to tumble, Box Hill struck the first blow of the third stanza before the Seagulls rebounded strongly to claim the lead for the first time in the match.
But the momentum was short-lived as the Hawks shined under dark skies when it mattered most.
Collins said he was pleased with the endeavour of his players after quarter-time.
“Obviously in wet weather footy it’s hard once you lose the lead, but we probably could have done a few things better in the last quarter. A couple of mistakes were costly,” he said.
“We still need to improve as a team and under pressure.”
The coach heaped praise on Ben Davies, who never stopped running, while Adam Marcon gathered a heap of possessions and kicked two goals in as many minutes in the third quarter to ignite his team’s charge.
Ruckman Nick Meese was also impressive, along with skipper Ben Jolley, Jack Johnstone and Kane Lambert.
The result leaves Williamstown at 6-4 ahead of Sunday’s clash against Sandringham at Burbank Oval.