Just as Jesus said to those Sadduces, at Matthew 22:29: "You are mistaken, because you know neither the Scriptures nor the power of God."
Yes, power of God...you seem to ignore that... the Noachian Flood was a divine event! He caused the two separate 'oceans' of water -- those above the Earth, and those below, in "the vast fountains of the deep" -- to break open; He brought the animals to Noah; He closed the Ark's entrance; He gave Noah those ideal ratios, along with all other instructions, to build the vessel.
For you and others to think that He did nothing else to protect them during the event, is simply unreasonable.
Jehovah could've put them in a bubble and just levitated them. But Jehovah always wants people to show their faith in Him when possible, acting in their behalf.
By providing Noah those instructions containing the ideal proportions, it not only allowed Noah to express his faith, but
revealed that it was from a Divine Source.
Tell me...can you come up with better ratios of length to width to height? Maybe you think the Ark "cube" in the Epic of Gilgamesh is feasible?
Better ratios are meaningless when a ship that big held together by wooden pegs will not work.
Despite modern technology no one has built a ship like this that even floats fully loaded.
Still waiting . . .
The contemporary ships cited had steel structural support. There was no steel nor even iron at the time the ship was claimed to be built.