Yeah, he knows that. His point is that it’s pretty odd that humans are so close to the neutral buoyancy point such that individual variations in muscle mass can tip the balance. If human buoyancy was random, we would probably be very buoyant or very not buoyant.
Not really that odd, considering as how we’re like 60% water or something like that.
No
Haha, displacement. I actually read something that I think is interesting relating displacement to global warming. The oceans will actually not rise due to any melting the the Arctic Ocean because the weight of the ice already displaces the same weight of water (water expands when frozen). However, the oceans will rise in proportion to the new ice that is on land melting. So, the oceans will rise due to the melting of ice on Greenland, Antarctica, etc. but not due to the melting of the Artic Ocean, which will create new shipping routes and unleash long dormant leviathians and will eat the world (not sure about that last part).
You must be black. I can’t swim either.
why don’t black ppl swim? they would win…as usual! 
Few people have pools in the ghetto. And black folks live in the inner city away from ponds, lakes, and rivers.
Knowing how to breathe properly is extremely important. Most people overlook that. I know a few people who gave up on swimming because they felt they couldn’t breathe comfortably.
Coordinating limbs movement with breathing seems to be the hardest thing to master for learners but can be achieved with practice.
Also, as someone pointed out earlier, 5 one hour sessions will do you a lot more good than a 5 hours marathon session
before learning to “swim” as in do laps you need to spend plenty of time learning to get comfortable in the water. Swimming is about balance. Your lungs are basically an interal floatie implanted in your chest- you have to learn how to pivot and move your body along this balance point to be comfortable in the water. Typically- someone who has does not know how to swim has greatest difficulty gaining this “feel” for the water, especially because many of the natural reactions inherently work against it. Like hyperventilating and breathing shallowly (decreasing your boyancy); reaching your head up for air (putting you vertical in the water), flaling your arms and legs (sinking you). So many of the things that put you in balance are counter-intuitive and thats what is tricky. You can be a 220 brick of muscle and float with no movement if you understand your relationship with the water, I had some (black) teammates that had this build and swam olympic trail qualifying times.
Before taking any sort of class just go to a pool, find a 4 foot section, and practice getting comfortable. Lay on your back and feel your chest float, note how when you reach your head BACK, sinking your eyes below the water line, you you can still have your mouth in the air but you can float. practice sculling your arms- moving your hands in a figure 8 and feel for when you have resistance against the water vs when you just cut through it. Do the same with your legs. Practice being FLAT on the water and breathing in a relaxed manner… once you get comfortable practice rocking to the left and right (while on your back) and putting some weight in your hands… if your pool has a gutter you can stick you heels in it to help your balance as you develop the comfort. After you have “the feel” you can go take a class and learn how to do it face down.