I have just found a site where there is some discussion of the ark's capabilities:
Page not found – — ’ ’
You will see that it is claimed that it was tested in a tank, and passed stability tests - I would like to see the assumptions which were made about loading! I suspect that the stability tests were pretty meaningless - they would just show that a weighted plank of wood would float. And of course there is a difference between a ship surviving a 90 degree excursion and the animals in it doing the same!
It is also pointed out that all calculations suggest that the ark would break up in heavy seas, so 'gopher wood' must have been much stronger than any other wood, or perhaps iron was used. Perhaps their design was much better than ours. (Perhaps Isambard Kingdom Brunell's great...great grandfather was consulted!)
There are huge issues about all aspects of the ark - provisioning, waste management, etc. I am interested in the loading - a critical aspect of todays ferries. I suspect it could not be done in the time available with the staff available, and I have grave doubts about the sea-worthiness of an ark with a large door in it.