Minecart gets invisible under water when seen from above the water in certain angles with 3rd person and when disable the GUI..

When a minecart its inside the water it gets invisible when seen from above the water but just in certain angles.

The same happens when you are inside the minecart and watch in third person above the water (again, just in certain angles).

Also, sometimes the nearest minecart gets invisible when disable the GUI with F1.