Tsunami spell cast in the air

Question

Let's suppose a spellcaster casts the Tsunami spell 100 feet above the ground. The spell description says that it originates at a point in range (sight) and does not say that it needs to be supported. Suppose that a flying creature, able to fly by the fly spell, is caught by the wave. What would happen if, while inside the wave, the fly spell ends and the creature is not able to fly anymore?

1. The creature remains suspended in the water in the air, and when the tsunami spell ends the creature immediately falls.

2. The creature falls immediately after the fly spell ends.

Answer 1

They will remain in the water until they move outside of it, or the spell ends.

According to the Tsunami spell (emphasis mine):

A creature caught in the wall can move by swimming. Because of the force of the wave, though the creature must make a successful Strength (Athletics) check against your spell save DC in order to move at all. If it fails the check, it can't move. A creature that moves out of the area falls to the ground.

This seems pretty straightforward. The water wall is actively keeping the creature within it until the creature moves out of the wall via a Strength (Athletics) check, or the spell ends. When a creature moves out of the area, they fall to the ground, implying they are kept aloft until then (which makes sense if the water is pushing them). When the spell ends, they are subject to whatever gravitational forces they normally would, although if their Fly spell has ended, they will likely fall if they don't cast it again, or have any other method of flight.