How Sonar is revealing the secrets of the sea, lakes and rivers.

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Great work Paul. I was in the Hydrographic Survey division in the Navy. As an engineer, supporting the Hydrographer's who were mapping the seabed and gathering data to produce charts, it was quite an interesting time, although we spent months at sea working 7 days a week. I would be interested if you were able to do a similar video, based on the mapping of the sea bed using LIDAR. These were fitted to planes, along with large data collection hard drives and effectively put our method of chart making obsolete. I would think that we know a lot about our off shore sea bed, but very little further out to sea. My last stint at surveying was to help update charts, produced by Captain Cook!

That missing jetliner is also probably in a thousand pieces, too, even if you find it you might not know what it is at first.

I'd love to see marine archaeologists scan the sites of ancient naval battles like the Battle of Actium or Cape Ecnomus! Ok, it's possible that most of the ships may have rotted away but you'd think there must be something down there, even if only a few of the metal rams they had on the bows of their ships. I'd love to see a sonar scan of the seabed in the area of these battles!

I've seen experiments with dolphins that support the theory that a dolphin can recreate what the returns sounded like when it "saw" something interesting previously and wants to "show" another dolphin. It would be like us recreating a tree or a landscape by projecting a hologram of what we saw for someone. Also, they were recording the sounds that drove Chladni plates. Not with a bow but with a transducer. They threw a hoop, a square, a four bladed propeller shape and s star made of plastic tubing into the pool and then played the sound that jostled the sand on the plate into a square. The dolphin swam to the square hoop and bought it back! So the dolphin was turning the sound into shapes in its brain! I was thinking that to recreate the returns from an object too show another dolphin it would have to recreate what it sent as well as the returns otherwise the second dolphin wouldn't be able to tell exactly how the object modified the sound, distorting the "image". Fascinating stuff!

Man, seeing that ship rollover, brought about some anxiety. I couldn't fathom still being inside that ship when it rolled and went belly up. Had to have been absolutely terrifying.

We missed you, TechnoVarys

Water isn't actually incompressible, at oceanic depths, it can be compressed 4 to 5%, which is enough of a spring for explosive decompression (speed of sound in water) instead of just freefall speed. Just an interesting factoid I learned after the whole Oceangate thing.

It's astonishing how much can be heard, even by primitive passive sonar. For anyone interested, take a listen to the sinking of Japanese submarine i-52 in 1944. it's the only recording of a sub being sunk by an acoustic homing torpedo. Despite the quality not being great, the actual detail is chilling. The sounds of inrushing water and subsequent multiple implosion events as internal tanks and piping are crushed by ever increasing sea pressure, is fascinating and horrible at the same time. Worth a listen, even if to appreciate how much can be heard underwater.

"...JUST 4km down under the ocean." Understatement of the year. Ty as always for the content!! <3

As someone who spent 20 years being a sonar technician (surface) in the USN, I'd just like to tell you how much I enjoyed this video. Learned a couple of things also. I never knew what they were using for crystals in the early sets, that was one. Also, while the acronym ASDIC was mentioned briefly in our rate training manuals, I can't remember an explanation of what the acronym stood for. Probably because it was so far removed from the time I served (79-99). Another thing I would like to mention is that in 20 years of operating at sea, primarily in the Pacific and Indian Oceans, including every sea contained therein, I never once heard a U.S. submarine go active on sonar. Mostly never heard U.S. subs at all, just a couple of times. The only submarine I ever heard go active was a Charlie class Soviet SSGN who lit us up with his Blocks of Wood fire control. The Charlie was submerged and in company of a couple of Soviet destroyers and the Russians routinely f'd with us by lighting us up with every radar, fire control radar, and whatever else they had. All they really did was provide us with intel on their systems while we remained quiet. Definitely will be sharing this with my sonar group.

Hey Paul! Hugely enjoying your presentations. I'm a science and engineering buff and your presentations are brain food for me. Keep going!

Wonderful work Paul always enjoy your videos.

Great Episode. One of the few Youtube channels with accurate information, clearly presented and quality audio/video, including rare archival media. Spectacular. Topics are always interesting too!

In case anyone is interested, Adventures With Purpose is a YouTube channel about a couple of guys who work with law-enforcement agencies in the US; they use side-scanning sonar to identify possible targets for missing-persons cases, and they then dive the targets to determine exactly what it is they've found.

Several sonar systems are used by subs, a short scatter sonar dectects mines, sea ice, or even dead whales. Sonar systems are so sensitive you can hear shrimps clicking their claws. However there are also massive blind spots, in recent years a sub went to surface and had a massive commercial ship approaching from the rear, the sub came to periscope depth and did a visual sweep and had to do an emergency dive. She got hit and did damage to the conning tower. Amaazing tech but still fundamentally flawed in so many ways...

TOP NOTCH as always! I love your work!

'Back in 2010' Man, how did we even get through the day !

I guess Pauls feeling better! Well done Paul!

Out of curiosity, have there been any studies done on the damage a 200db in water sonar system can cause to whales and other marine life?