CLAY COUNTY, Fla. -- A first-of-its-kind boat that doubles as a submarine was tested Friday afternoon at Kingsley Lake, which is west of Camp Blanding.

At first glance, some onlookers would probably think the test was a million-dollar ship sinking. But that was not the case. The Hyper-Sub Submersible Powerboat is a combination boat and submarine that is supposed to go underwater.

Developers said as a boat it can hit speeds of up to 35 mph, and as a sub it can go 5 mph and as far as 600 feet under water.

The Hyper-Sub has been inventor Reynolds Marion's life work.

"I started designing it when I was about 11 years old and spent 31-32 years trying to come up with the solution that make that type of a design possible," Marion said.

The Hyper-Sub is not going to be cheap. When it's put on the market, the starting price is expected to be around $3.5 million.

Reynolds said the Hyper-Sub would be a hit with everyone from the military to would-be explorers.

"You can use it across all sorts of different markets, like oil and gas, military, charter services. You can even own them as a retail private owner and you don't have to have a support system," Marion said.

The Hyper-Sub sports two-inch thick, iron reinforced glass to keep things safe inside during a dive.

"The first few times it was kind of scary. I was getting claustrophobic when the water would come over the top of the cabin where I could see. It was a little scary, but now it's kind of routine and most of what I think about is how much better we could do on the next one," said engineer Scott Shamblin.

Marion said now that his demo is up and running, his company has proved a lot of people wrong.

"Most of the submersible engineers we spoke to before we started building this told us that this was not possible for one craft. So we made history," Marion said.

Developers said they hope to have Hyper-Sub on the production line sometime in the next couple of years.