The Socceroos fell behind to a wondrous strike from Christian Eriksen, before equalising when Mile Jedinak converted a penalty for the second game in a row.
Van Marwijk's side improved significantly in the second half, but suffered frustration as they chased a goal that would have significantly boosted their hopes of qualifying for the round of 16.
"It's unbelievable and a pity we didn't score more," Van Marwijk told a news conference, assessing his side's failure to score again.
"In the first 15 minutes we were a little bit restless but after that we started to play football and had confidence on the ball. We controlled big parts of the game and in the second half we created chances."