[kortilla]

> Boats, especially the larger ones you see being used for fishing/shipping generate a lot of noise due to powerful engines and underwater cavitation caused by their propeller spinning.

A couple of things. First, that video shows you how relatively quiet the ships are unless you are right underneath the back. You can’t even hear the engine noise towards the front of the ship (which is likely why a ship the size of a city block snuck up on a scuba diver).

Second, propellers on those ships don’t cavitate unless they are misconfigured. Cavitation is inefficient and causes vibration the shipping companies are absolutely incentivized to eliminate.

There are many problems with commercial shipping (the pollution, etc), but the noise is not realistically one of them.

The much bigger noise problem is sonar.

[scubazealous]

That diver did not have the ship sneak up on him, he was diving in a shipping channel and knew there would be a ship coming up. He prepared by staying next to the large chain on the bottom and holding onto it so he would not be sucked into the propeller. In addition, the reason the ship did not sound "loud" to you is the way gopro records audio. Had this been recorded with a calibrated hydrophone the noise would have been off the charts.

I agree with you the bigger problem is sonar but I hold my opinion the whale in the video swims how it does because it is avoiding the sound of these ships, it is not acting on sight or attracted to wakes/ plankton.

[runarberg]

Sound travels differently underwater. A diver senses every sound as if the source is from their own head and all sound sort of blends into one. A whale has a much easier time distinguishing different auditory signals underwater then a diver does. Furthermore, a whale can probably sense the direction the sound comes from and how fast it is moving. A diver failing to notice a giant ship is no evidence that a whale will.

[kortilla]

The video was meant to show how loud ships were. It did not.