Answer: They are directly caused by the gravitational pull of the Sun.
Explanation:
Water waves are caused by a whole number of factors, they include,
1.) Local winds
2.) Distant wind
3.) Air pressure
4.) Seismic sea wave
The gravitational pull of the sun and moon on the earth also causes waves. Although the sun's gravity also contributes to the waves, but its effects are smaller and serve mostly to vary the heights of high and low tide.
