An ark has no power plant or navigation aids.
Ergo
The ideal ark would have a hull shaped like a wide parabola and a bow on each end that slopes in toward the ship and not away from the ship which 100 % of cruise ships today unfortunately have.

This self correcting configuration would behave in changing currents nicely.
But the roll & spin effect on the passengers would be brutal.

Buuuiiicckk

EUUrooope