Algodoo

This is an example of a way to make a water door. water doors cant be made in real life but there flexible offering easy door replacement

Controls
Numpad 1 and 2 for extra water
left and right for car
up and down for water release

Tip for one enter/exit only, release water, drive in the middle of the door and add water it will go ontop and sit there until you drive through and it will go down then lock