Philippe Coutinho and Mohamed Salah fired Liverpool into a 2-0 lead in London, only for Alexis Sanchez, Granit Xhaka and Mesut Ozil all to strike in five minutes to catapult Arsenal into an unlikely lead before Roberto Firmino's goal salvaged a point for the visitors.
Less than two minutes later, Salah seized upon a terrible Leroy For backpass to set up an easy tap-in For Firmino. After the game, you look and it's 5-0 and you think: 'Wow, 5-0.
Coutinho, who was strongly linked with a move to Barcelona in the build-up to the season, has enjoyed his most prolific goalscoring month in a Liverpool shirt, finding the net seven times in December.
Swansea mounted a counter of their own as they sought to mount a quick response, but a tame Wayne Routledge header produced a straight-forward save for Mignolet.
A minute later Firmino tapped into an empty goal from Salah's square pass before Oxlade-Chamberlain completed the rout.
Coutinho's arcing shot from the edge of the penalty area which had just enough curl on it to take it inside the far post. There are points Liverpool should not have won but we did get them.
Alexander-Arnold's milestone goal arrived when he charged into the Swansea box, latched on to an Alfie Mawson clearance and rifled a shot of the underside of the crossbar.
The win over Swansea saw Liverpool climb back above Tottenham and into fourth place, leaving Klopp to emphasise the quality of his players' performance after a challenging first half. I could have done better with my end product a few times. "At the end he scored two goals so that's nice, very nice".
Liverpool boss Jurgen Klopp is holding talks with Simon Mignolet about his current form. "The first half was not too bad: we grew into game, got a little bit of confidence, but after we conceded the second goal all belief and confidence drained from the players".
Salah is now the first player this season to have been involved in 20 league goals this season, with his fifth assist of the term.