They built a submarine
From tuna cans and tape
To do the deepest diving
To see the oceanscape
Down, down, down through wet unknown
They sunk below like people stones
Longing to see exotic creatures
In a homemade sub with shoddy features
At the bottom of a rocky fissure
They learned an awful lot about pressure
Three miles down where sub hit ground
There was no time to look around
For the ocean piled upon the ship
Made metal bend and tape go rip
A squishy end to a perilous trip
A crew squeezed out as people drips
They floated back up to the top
A pressure pasted pile of glop
Water pressure can be a beast
Human bodies can't bear the least
But tell your mother not to worry
The sub I made is much more sturdy.
-B.C. Byron

Another science poem, and you can expect more. Water pushes from all sides and it pushes harder as a submarine, fish, or human diver goes deeper. I saw a science show once where they tested water pressure with an old fashioned, metal helmet diving suit. They filled the diving suit with meat and sent it down into the deep. As soon as the air hose was closed off, the pressure from inside the suit was less than the ocean pressure outside and GOOSH! The meat turned into liquid and squished up into the metal helmet. Yuck! Water pressure is a powerful force.
Another cool experiment I saw involved shooting a bullet into water (don’t ever do this). The water pushes back on the bullet so hard that it stops within a few inches of water. Bullets from higher powered guns had even less effect in the water. The bullets fell apart into tiny bits from the force of the water. Water is chock full of great physics lessons.
So how do fish stand all that pressure when a metal submarine can only go down so far without crushing? How can they survive even 4 miles down in a deep ocean trench with thousands of pounds of pressure on all sides, constantly? I leave that puzzle to you to ponder. Just try to solve it before you go to Google to get the answer.
Once in a while I like to slip in some real science in my poems, but there is always some good fun. Thanks for reading.