The former South Canterbury man was competing in heat two of a national powerboat racing event on Sunday when the hydroplane he was driving, known as The Boss did a complete flip and landed upside-down.
Hart was trapped in the boat for several minutes as it filled with water. However, he said it was a good example of the safety apparatus working correctly.
"I'm not going to lie, the first 30 seconds or so underwater were pretty scary, but once I knew the breathing apparatus was functioning, everything was OK."
Hart was able to latch on to the breathing apparatus as the boat filled with water.
"This isn't going to stop me racing again. I'm getting ready for an event in Twizel [in February]."
Hart said the boat went from 80kmh(49.71 mph) to more than 220kmh(136.7 mph) "in under three seconds", but for some reason, it could not maintain the speed and got caught in the wind.
"It just went airborne. There were two other boats alongside me, they didn't get touched at all," he said.
"The damage to the boat is mostly cosmetic, we'll be able to put it back together again. It's made out of strong Kevlar material."
The safety boat with divers was quickly to his aid and helped him to safety.
Race organiser Denise Moughan said it was hard to process what happened.
"Debris was flying everywhere, it was terrifying. Ray did everything right from a safety point of view," she said.
"It all happened so quickly. The racers hadn't even reached the first corner. He was very lucky, it could have been so much worse. But he loved the speed. As soon as he emerged without a scratch, he wanted to help with the boat's recovery."
Moughan said the boat's cockpit was similar to one featured in an F-16 jet.
"That means it was really safe inside. These boats are built for speed," she said.
Hart, who said he was in his 50s, spent most of his life in Otaio, but moved to Christchurch about two years ago. He had been racing hydroplanes for about two years.
"There's nothing else like them, you will not see anything faster on the water. I'm not going to let that incident stop me from racing again.