After a powerful Matt Simon header before half-time, the Mariners conceded twice within eight minutes to drop the three points they had safely in their hands at the main break.
The Mariners scored after Michael McGlinchey took the ball down the left flank before it was knocked out for a corner where McGlinchey played in Nicky Travis for a short corner and then supplied a lovely cross. Matt Simon was loitering at the back post and powered a header home under extreme duress from Kristian Rees that took the home side by surprise.
United managed to equalise in the 68th minute when Andrew Barisic turned United forward Joel Porter and chipped it back in for Shane Smeltz who nodded it home with ease.
Five minutes later, the home side should have been in front when midfielder Zenon Caravella played a ball through to Smeltz and the Kiwi knocked it home but the linesman called for offside much to the dismay of the home fans.
But almost a minute later, Jason Culina made a ghosting run down the middle before unleashing a shot on Mariners goalkeeper Danny Vukovic who made a brilliant save but the 23-year old Barisic was on hand to knock it in from close range.
Gold Coast managed to come back from a goal down to grab three points to jump into outright third on the table and poise themselves for a shot at a top-four finish in just their first season in the A-League.