So if I know what buoyancy is you suddenly going to start listening to me?
Supposedly gravity is strongest at the gravitational center, so if gravity cannot pull helium down at the surface of earth, it will not be able to pull down helium up in the atmosphere, helium is not gaining any weight the farther up it gets.
Something is wrong with your model, you just don't want to admit it.
Chances are no Great Whites will show up. If they did it just be one of the remote controlled animatronics. Sorry what you experienced was a hoax, if you expect it to be real it will appear real to you, just how our mind works, it bends the truth based on our expectation.
A fish can bite you while snorkling, but only if provoked, if this happens just keep on swimming away. We have a tendency to remember things worse then they actually were if something bad happens, for all I know you might have just stepped on a rock.
Just because Great White Sharks and Orcas are not real doen not mean we are in a simulation. I dont know why that is the takeaway from what I said.
Only Orcas you can swim with are animatronics. Here is a video of how lifelike they actually are:
No Great White Sharks are in any aquariums. No sharks will attack you, that is just a lie you been told.
I leave the youtube video watching for children to you.