Ocean Exploration

Season 05

Episode 09

✓ Link copied to clipboard

Most of our planet is not the land under your feet, it is the water off the coast, and it is very hard to reach. In this episode of Bill Nye the Science Guy, Bill peels the ocean off a giant globe to show that 71 per cent of Earth is ocean, then dives into how pressure, darkness and salt water make exploring it a serious engineering problem, and how submersibles and sonar have started to solve it.

In this episode you will discover:

Why the ocean covers about 71 per cent of the planet, and roughly 75 per cent once you add rivers, lakes and streams
How water pressure increases the deeper you dive
Why a long snorkel does not work no matter how hard you breathe
How SCUBA gear feeds high pressure air to a diver’s lungs
Why sea water rusts metal and corrodes ships, so vessels must be hauled out to be cleaned
How the ocean floor has mountains, canyons and underwater volcanoes, and how sonar and weighted lines are used to map them

Why exploring the sea is hard

Bill’s core point is that humans are land animals in a mostly ocean world. Underwater we cannot breathe, and every ten metres of depth adds roughly another atmosphere of pressure on our lungs, so we need machines. A snorkel only works to a few centimetres, because the pressure of the water on the chest quickly overwhelms the pressure of the air at the surface. Scuba gear, submersibles and ships turn ocean exploration into a proper engineering discipline.

Key concept
Ocean cover
About 71 per cent of Earth’s surface is ocean, and around three quarters is water once rivers and lakes are counted.

Key concept
Water pressure
The weight of the water above you grows steadily with depth, adding roughly one atmosphere of pressure every ten metres.

Key concept
Sonar and mapping
Sound pulses bounced from the sea floor let ships build detailed maps of underwater mountains, canyons and volcanoes.

Bill Nye’s demonstrations

Bill peels the ocean off a giant globe of science to show how little of the planet is dry land, then uses stacked coins on kitchen scales to model how the column of water above you gets heavier the deeper you go. He straps into a long snorkel and tries to breathe through it under water, which fails because the outside water pressure is too great for surface air to flow down the tube. He then switches to a SCUBA rig with a high pressure tank, and finally shows a rope and weight being lowered from a ship to sound the depth of the sea floor.

Try this at home

The three hole bottle test. With an adult, take an empty two litre plastic bottle and carefully make three small holes at the same height in a vertical line, one near the top, one in the middle and one near the base. Cover the holes with tape, fill the bottle in a sink, then pull the tape off. The water from the bottom hole squirts out much further than the water from the top hole. The deeper the hole, the more water pressure is pushing the jet out, in the same way that the deep ocean is under much higher pressure than the sunlit surface.

Cool facts

Ocean covers about 71 per cent of the planet, and once rivers, lakes and streams are added, roughly three quarters of Earth’s surface is water.
Sea water is around 3.5 per cent salt, which corrodes metal so quickly that ships have to be hauled out and cleaned regularly.
At the deepest known point in the ocean, in the Mariana Trench, the pressure is about 1,100 atmospheres, more than a thousand times the pressure at the beach.
Human eyes cannot see the bottom of the deep ocean, because sea water absorbs all wavelengths of sunlight within a few hundred metres.

Science update: since this episode aired

The Nippon Foundation and GEBCO Seabed 2030 project, coordinated internationally through the Intergovernmental Oceanographic Commission of UNESCO, announced that just 6 per cent of the world’s ocean floor had been mapped to modern standards when it began in 2017. By 2025, that figure had risen to more than 27 per cent, with over 4 million square kilometres of new sea floor added in a single year. UNESCO Intergovernmental Oceanographic Commission, 2025
The Nippon Foundation and the UK based Nekton Foundation Ocean Census have run 13 deep sea expeditions in a single year, involving more than 1,000 researchers across 85 countries, and announced 1,121 new marine species in 2026. The finds include a ghost shark relative in the Coral Sea and worms that live inside the silica skeletons of glass sponges on Japanese volcanic seamounts. Nekton Foundation, Ocean Census, 2026
Researchers at the University of Tokyo have used tiny chemical fingerprints in less than one millimetre wide larval shells to track how deep sea creatures move between hydrothermal vents on the ocean floor. Some larvae may spend more than a year drifting near the surface before settling back down at a new vent site kilometres away, revealing an epic and previously hidden migration in the dark parts of the ocean Bill talks about. The University of Tokyo, 2026

🎓

Curriculum focus

Built on NGSS MS-ESS2-2 and MS-ESS2-4 (Earth’s systems and the cycling of water). Complementing that, it is pitched at KS3 geography (oceans and physical environments) and works as an introduction or revision aid for GCSE and IGCSE physics on pressure and geography on water and coastal environments, across boards such as AQA, Edexcel, OCR and Cambridge IGCSE. The worksheet and critical thinking questions take these ideas further than the episode alone.

NGSS MS-ESS2
KS3 geography
GCSE revision
IGCSE revision
Oceans
Water pressure