Eddie Howe's men had slipped alarmingly down the table having not managed to keep a clean sheet since a New Year's Eve victory against the Swans.
In the time since, they had shipped 26 goals and taken just six Premier League points as they were dragged into the battle for survival.
Last weekend's 3-2 win over West Ham was fraught with tension but against Paul Clement's Swansea the defence stood firm and was largely unchallenged, and Cook knows that is no coincidence.
"A clean sheet has been a long time coming," he said after Saturday's 2-0 victory over the Swans.
"It's been since Swansea away on New Year's Eve, which is far too long and we've conceded a lot of goals.
"As a back four we've been working really hard in the last couple of weeks and ever since Manchester United we've looked very solid.
"I'm delighted, it's like scoring goals when you're a defender so a clean sheet is huge for us."