Consider a Simic Hybrid with the Manta Glide trait:
You have ray-like fins that you can use as wings to slow your fall or allow you to glide. When you fall and aren't incapacitated, you can subtract up to 100 feet from the fall when calculating falling damage, and you can move up to 2 feet horizontally for every 1 foot you descend.
If the Simic Hybrid were to fall from a 50' height while not in combat, it could unequivocally move 100' horizontally as it falls those 50'.
However, I'm unclear what should happen if the Simic Hybrid falls during combat.
Can the the Simic Hybrid move 100' horizontally while falling 50' feet even if its speed is less than 100' or even if it falls during someone else's turn?
If not, what happens?