View inside a bubble sub

The best way to take in undersea sights may be in a giant bubble! Called bubble submersibles, which are clear, spherical subs that debuted in the 1970s. But these underwater crafts have only recently become a popular choice for marine-life fans.

That’s because engineers have figured out how to make the bubbles out of plastic. Early bubble subs were made of glass, which was difficult to shape into a perfect sphere—and expensive.

“Today, all bubble subs are made of acrylic,” says William Kohnen, the president of Hydrospace Group, an engineering firm focused on sea exploration. Acrylic is a thick plastic that can hold up to the pressure of the ocean while providing stunning views of what lurks below the water’s surface.

“When you sit in there, you will not see where the acrylic ends and the seawater starts,” says Kohnen.