The Reds scored first through Iain Fyfe seconds before half-time but were then put under plenty of pressure by a determined Mariners unit and in the end were forced to take just a point home when Matt Simon scored with six minutes remaining.
Coolen said it wasn't such a bad result, especially being on the road.
"At the end you're happy with one point. Before the game, if you're playing away, a result like this is not negative but we came for three points and in the first half we did well, we created a number of chances," Coolen said.
"When a team is playing at home, they will change a few things with the way they play at half time, we knew that and we had to look at ways to try and keep possession and wait longer for the chance to score a second goal."
Adelaide now have two draws from their opening two matches and will now prepare to take on Melbourne Heart at Hindmarsh Stadium on Friday night.