The incredible nature scene played out Wednesday just after sunset in Newport Beach ... but the footage, captured by photographer Patrick Coyne, didn't start spreading like fire until it was posted Thursday night by a popular whale watching company.

Coyne, who also recently shot bioluminescent waves crashing the shore, said it was incredibly challenging capturing the dolphin vid ... trying to spot what you're looking for in pitch black conditions. It almost didn't happen.

As he put it, "We were out for a few hours and on our final stretch back we finally had 2 dolphins pop up to start the incredible glowing show."

So, what makes them glow? Well, obviously it's caused by algae in the water around the dolphins. Duh!!! (Yeah, we Googled).

According to National Geographic, bioluminescent phytoplankton is what gives the surf its electric blue glow. The bioluminescence could also be a form of self-defense for the algae.

Whatever. All we know is it looks REALLY cool!!!