Well... The diver who went down to inspect the bottom of the ship came across the hull of another boat.

They're sending a diver down. Muddy bottom down there, ain't it?

Scuba divers can't get there, submarines go right on past it.

I've made hundreds of dives in submersibles.

Like in a submarine, underwater?

444. The need for obtaining better information about the ocean floor has led to recent advances in diving apparatus, submersibles, remotely operated vehicles (ROVs) and self propelled autonomous underwater vehicles (AUVs).

But the divers are still looking,

They sent a diver down. He found another boat.

So you can imagine scuba diving here.

We know he's been taking girls out by boat.

But, the point is that scuba divers generally stay less than 100 feet deep, and very rarely go much below this, at least, not with any kind of sanity.

The diver made another discovery.

What is this sister of yours, a deepsea diver?

Diving day and night was really easy for me in 1970, when I led a team of aquanauts living underwater for weeks at a time at the same time that astronauts were putting their footprints on the moon.

It's been considered, Sir.

Ah, ama . Diving girls.

The problem happens when you start to go underwater.

Suddenly, Richard went under, not diving, but the way seals do, just sort of settling in the water.

In each mission, we embarked scholars and specialists from universities, museums and laboratories.

When I first went to the Maldives, dead keen on diving, spent as much of my time as I could in and under the water.

Man your debark stations.

There're three basic limitations of scuba diving.

Can you swim underwater?

A dive more.

Dumas and Falco leave for explore the twilight zone at the foot of a cliff coral.

No, I don't want to die! I haven't done a thing.

I'll jump for it, I'm at home in the sea.

If you look at this diagram of a coral reef, we know a lot about that part up near the top, and the reason we know so much about it is scuba divers can very easily go down there and access it.

But let's also think, as a visual species, what it's like when we go snorkeling or diving and try to look underwater.

This is why a man who descends to the sea, per meter down

I'd dive...

What about the submarine?

Stand by to winch in the submarine.

How about some skin diving?

There is a problem with scuba though, in that it imposes some limitations on how deep you can go, and it turns out that depth is about 200 feet.

The recently developed AUVs are computer guided, untethered vehicles, capable of overcoming many of these problems, but are expensive.

They can dive to a depth of 1000m. They have jaw, teeth, and They feed on squid or cuttlefish.

But scuba diving, submersibles and all the work that we're setting about to do here will help rectify that.

Is the submarine there?

Look! Nautilus is just leaving.

So if you ever, ever get an opportunity to take a dive in a submersible, say yes a thousand times, yes and please turn out the lights.

And I talked to divers that had been diving there for many years, and they said that the marine life was better here today than it was in the 1960s.

The only creatures that have got conscious control of their breath are the diving animals and the diving birds.

For example, operational performance and survey capability of a new type of relatively inexpensive AUV has been demonstrated at a depth of 600 metres.

These birds make a living by diving into the water.