I think of the wave action as cyclic in the sense that it will cause the tip of the jib to swing up and down (or whatever).
But the nature of the effect of the waves on a heavy object with a varying centre of mass (as the load is lifted or slewed) seems like it would be very complex indeed.
Even in flat-calm water the act of lifting a load or slewing the jib will cause the deck to oscillate. I have no idea how you would distinguish crane-induced oscillations from wave induced oscillations.
Could you use a second sensor on a nearby small lightweight floating platform to detect the natural movements of the waves?
Presumably with that 6050 device you could record angles to your heart's content. But what then?
Perhaps if you explain why you want to do this your project would be easier to understand. I presume it has nothing to do with the crane falling over.
...R