While you are playing frisbee in the surf zone with another person, your friend watches while sitting on the beach nearby. after a while, you look up at the beach and realize you are no longer directly in front of your friend, who remained stationary on the beach all the while—you are still in the surf zone, but 30 to 40 yards from where you started. what is the correct reason for this movement?

The waves were coming at the shore from an angle, and they pushed you away towards that angle. See explanation below.

Explanation:

This is a common situation while being in the ocean.

This situation happens when waves come at the shore from an angle, therefore, the general current of the ocean switches to that angle and while you are "standing" in the ocean, the current is actually moving you towards that direction so you end up moving to one side of the other depending on the waves' angle.

Thus, while you are playing Frisbee in the surf zone the waves were coming from this angle who made you move so you no longer stand in front of your friend but 30 to 40 yards from where you started.

i feel as if they would both catch on before to long because they would see them to frequent