?The Magpies were unable to recover from a poor second quarter, which saw the side only manage three goals to the Bays' six, despite a promising start to the match.
When the rain started in the second half, it was Glenelg who was able to withstand the conditions.
Port Adelaide flew out the blocks, with the likes of Danny Butcher, Tom Clarke and Ben Sawford breaking through the centre clearances, all keen to make amends for last week's missed opportunity after a draw with North Adelaide.
Sam Gordon was first to boot Port Adelaide's first goal for the day, after a contested mark just outside 50.
Two more goals followed for the Black and White, all earned by the side's hard attack on the ball and hunger to win the one-on-one contest.
The Magpies' defensive pressure was at a high early and and the visitors dominated play with slick ball movement, fast running and hard tackling, pushing through the middle.
Port Adelaide's dominant first quarter saw the young side more than doubled the Bays' inside 50 count, (12-5), was not shown with any real scoreboard pressure and the black and white only led by two goals at the first break.
The Magpies' inability to make the most of its chances up-forward continued and the Bays made the visitors pay, as the ascendancy swung the home side's way in the second term.
Glenelg pressured the Magpies and gave the side little room to move and when in attack, Port Adelaide was forced into bombing the football long to a contest.
Despite the visitors' constant hard tackling, ball handling errors hampered the Magpies and Glenelg's forwards took charge to take a three point lead at the main break.
Ben Sawford and Tom Gray worked tirelessly to provide the forwards with opportunities to score, but Glenelg's defence and experience proved too much for the Magpies.
The second half was wet-weather football, as the rain started to pour down and it was Glenelg who worked better in the slippery conditions.
Glenelg's ball movement in attack was more precise, but the home side only recorded one more scoring shot than the Magpies in the third term.
The rain may have poured, but goals were hard to come by, as both teams suffered from poor kicking in front of the big sticks.
But the Magpies were out-classed in all the key statistics, as Glenelg recorded 10 more inside 50s in the third quarter and had more than doubled the visitors' clearances (23-47).
A goal to Jack Cooper and one to Cody Liernert on the siren were the Magpies only two majors for the final term, while the Bays scored five to seal the victory.
Port Adelaide Academy coach Jacob Surjan said after the game his chargers lacked a leader to help lift the side when the momentum changed.
Despite the loss and inconsistency, Surjan said there were some positives to take out of the match and the young side's development.
"The boys just went away from our structures and didn't follow instructions," Surjan said.
"We really need that Travis Boak or Steve Summerton type of player in our team to step up and show some leadership skills, but no one has been able to do that yet.
"Unfortunately when we moved away from our structures we were showed up by a classy Glenelg team.
"It's a work in progress and as disappointing as the loss was, there is a lot of positives in our ball movement.
"We proved that when we stick to what we know and the way we want to play anything is possible, but it's just being able to do that for four quarter and that's something we just can't get at the moment."
The Magpies will return to Alberton next week searching a third win of the season, in its clash with Central District on Sunday, June 8.
SCOREBOARD
PORT ADELAIDE 4.2 8.3 9.8 11.11 (77)
GLENELG 2.2 8.6 12.9 17.15 (117)
portadelaidefc.com.au’s best
Deeley-Godfrey, T Gray, Northeast, Williams, Sawford, Cooper
Goals
Lienert 2, Gordon, Northeast, Hawkins, Masters, Davidson, Sawford, T Gray, Deeley-Godfrey
at Glenelg Oval
