Austin signs as Mariners' rebuild continues
Austin was a Manly United junior before moving to England, where he has spent his career playing in the lower leagues.
The 24-year-old left-footer was happy to finally put pen on paper with Tony Walmsley's team.
Austin was at Cambridge United in League Two last season before numerous stints on loan.
The midfielder said he had taken plenty out of his experiences in England.
"There's quite a lot of long ball and fighting for wins every single week over there," Austin said.
"I think I've got to be a lot quicker on the ball as a result. I think here you get probably a bit more time and they let you play a bit, whereas over there it's take a touch and you're virtually getting smashed.
"Obviously I've gained a lot from that, I'm quicker and you've got to be smarter. I've gained quite a lot from it."
Austin describes himself as "quite quick" and a "decent crosser of the ball", and feels he will have no trouble coping with the physicality of the A-League.
He was on loan at Brackley Town in Conference North last season and returned to Cambridge before being sent out to Southport in Conference Premier.
He was released by United at the end of the campaign.
Austin's signing continues the Mariners' rebuild, with former Sunderland striker Roy O'Donovan having already joined.