Depor were losing 1-0 at Almeria when Aranzubia jogged upfield for a corner in the fourth minute of stoppage-time.
He had ventured forward once already, to lend his presence in the penalty area to a Depor free-kick but it came to nothing and he was forced to scramble back to his own area.
Moments later, though, he rose above the Almeria defence to glance the corner past his opposite number Diego Alves, denying relegation-threatened Almeria a vital win.
He was mobbed by his team-mates as he sprinted away to celebrate with his arms spread and a look of surprise on his face.
"You don't practise these moves. It's a question of luck and sometimes it comes off," he told Spanish radio.
"I've been up before but I've never scored a goal. I did what I have seen my team-mates do and tried to copy them the best I could.
"My coach was happy for me and for the point we won."
Almeria coach Jose Luis Oltra was not so happy.
"For them to score against you in this way, when the team has done everything to win, is a killer," he said.
