Waterjets don't work above the water even when supplied water either from an internal tank or a direct sea intake lower down.

In my scenario, my hydrofoil boat uses waterjets with sea intakes 2-3 meters lower going into a custom tank (22.5K litres).

When the waterjets are below the water the boat performs fine, when the waterjets are above the water they act like propellers and stop working only to work immediately once they are submerged again.