I have seen waves on the surface of the sea.
These were waves that changed over time, and an object that was on the surface (an empty plastic bottle) will go up and down with time, but NOT displacing horizontally.
If I could measure the difference between when the bottle was at the top of a rest or at the bottom, I would say that the "peak-to-peak) distance was about 4 feet, which would make the actual amplitude of the wave of a 2 feet magnitude.
The frequency of the wave movement was associated with how fast the bottle will swing up and down. If I recall correctly it would take a little more than a second to go from top to bottom, which will make the frequency of about one full cycle every 3 seconds: f = 1/3 (1/sec)