12 photos show how humans explored Earth's oceans from the 1600s to now

Named the "American Turtle," Bushnell designed and built the vessel in Connecticut as a machine for carrying gunpowder underwater to blow up enemy ships. In the depiction above, its first mission is manned by Sergeant Ezra Lee, who is shown opening the hatch after an unsuccessful attack. The auger visible in the image was used to drill charges into ships' wooden hulls.

While we've mostly focused on underwater vessels used for exploration in this list, the fact that many consider the Turtle the first submarine (since records of the Drebbel are so scant) made it worthy of inclusion. The Turtle could go about 15 feet underwater (4 meters).

Beebe and Barton conducted a series of dives with the Bathysphere between 1930 and 1934, setting a depth record of 1 kilometer (3,028 feet)in August 1934. This allowed Beebe to make the first observations of deep-sea life in its own habitat.

Before this, the deepest humans had ever gone underwater was around 525 feet. For that, people used an atmospheric diving suit that was armored to protect against the pressure.

For every 10 meters (33 feet) you go underwater, pressure increases by about 1 atmosphere, a measure of Earth's air pressure at sea level. That means 10 meters down, pressure is double what it is at sea level. One kilometer down, pressure is 100 times what it would be at sea level.

To withstand those forces, Barton designed a spherical submersile made of steel with windows made of three-inch thick quartz.

Barton designed the Benthoscope to withstand even greater pressures than the Bathysphere. His 4,500-foot descent off the coast of California remains the deepest a submersible suspended on a cable has ever gone.

Cousteau's Diving Saucer's name in French was the SP-350 — "SP" for soucoupe plongeante, which means "diving saucer" in French. The 350 referred to the depth it could descend: 350 meters (1,148 feet).

He called the vessel Denise.

The vessel used jets of water for propulsion.

They used a type of deep sea submersile known as a bathyscape. The particular model they first used to reach the bottom was named the "Trieste."

The Hercules ROV can travel 2.5 miles (4 kilometers) underwater.

Using an ROV to explore underwater is a game-changer because operating them remotely means the vehicles don't need space or life-support equipment for people. Because of that, an ROV is usually operating underwater 24 hours a day. (Pilots take shifts controlling it through a long fiber-optic cable.)

ROVs are used in industry, but Hercules was one of the first designed for scientific research, especially for the fields of archaeology, biology, and geology.

The Deepsea Challenger is a deep-diving submersile that Cameron piloted himself all the way down to the bottom of the sea.

The submersible has safely transported over 2,500 researchers on more than 4,800 dives to depths of 14,764 feet (4,500 meters).

While filming 1,500 feet (457 meters) underwater in Antarctica for Blue Planet II, the production team sprung a leak.

Luckily, they were still able to capture remarkable footage.

On that particular dive, they found that the waters beneath Antarctica are teeming with life. Using submersiles and ROVs, the Blue Planet II production team visited 39 countries on 125 expeditions, spending more than 6,000 hours underwater. While filming in the Mariana Trench, the deepest part of the ocean, they captured footage of an ethereal snailfish about 8,000 meters (5 miles) underwater, the deepest a fish had ever been spotted up to that time.