Same here, not commenting as a racist, just reporting the facts (this was in 1983).
It took years to figure out why Chimps could not swim. Then I saw a documentary on Animals that could not swim.
The theory is that chimps have so little fat the muscle and heavy bone mass just pulls them under.
Kind of makes sense as my Scottie Dog had such heavy hair she could not swim, just sank like a rock.
I had many a round with Dad that insisted that all dogs could swim. Why don't parents listen to their adult children.? Dad, dog sitting for me decided to throw a stick in a lake while telling my uncle that dummy me had told him MY dog could not swim. They stopped laughing when my dog sank from sight.
Both men fully clothed including shoes then had to jump in and save the poor dog.
Me I have the opposite problem, or had most of my life, At 90 pounds I had no muscle just skin and bone.
For me to dive and reach neutral buoyancy I had to have a good 80+ pounds of weights to dive SCUBA.
In a pool to hit 8 feet deep it was impossible for me to reach the bottom, Water displacement, I was like a piece of drift wood.
BYW quick sand is much like this, I was taught to throw myself on my back and swim with the back stroke out of trouble. Same as lake or sea swimming, water displacement. Same reason we have boats made of cement.
Some people have to be taught to swim and over come a body that that is for any reason too heavy to float in upright position. Never get into a boat unless you know where the life vests are and how to put them on. For small craft wear one before heading out anywhere where the water is over your head. It does not matter if you can swim like a dolphin, in a freak accident you can become dazed and discombobulated.