The Mariners reclaimed second spot on the A-League table despite finding themselves two goals down prior to the half-hour mark as impressive teenager Dimitri Petratos struck twice for the Sky Blues.
But Arnold's men rallied to record a draw thanks to goals from Patricio Perez and Matt Simon, putting them a point clear of Adelaide United and moving to within six of league leaders Brisbane Roar, and delighting their coach.
"The character in this team is unbelievable," said Arnold.
"They were out on their feet, and playing their fifth game in fourteen days, and to be 2-nil down at halftime any team with a lesser mentality could have thought game over and focused on the next game.
"To come back from that was very pleasing."
And Perez's performance was lauded by Arnold who feels the Argentine was the Mariners best on the day.
"I thought Perez was probably our best player today. I've said all along he brings something very different to our team," he added.
"That run he made for the goal today was the type of runs I saw him do in Argentina, and it's pleasing that he's now getting the fitness to do those type of runs. His goal today was a great first touch and a wonderful finish."