What is the cause of a rogue wave? I understand regular waves are the result of currents and wind.
Rogue waves are a function of harmonics. If a number of waves converge, and happen to be of a similar frequency and amplitude, they will reinforce each other to form one giant wave, which only exists so long as its component waves are converging. As they move past each other, they separate into the original waves again. Since the open ocean doesn’t really have a fixed “level”, it can be difficult to detect some of the larger waves, such as those caused by seismic activity or large storm systems over the horizon. However, if several of those large waves intersect, they basically climb over each other, and become visible during the interaction.