I know this phenomenon is explained by the Ekman spiral, which I partly understand. I understand that,

If the ocean is divided vertically into thin layers, the magnitude of the velocity (the speed) decreases from a maximum at the surface until it dissipates. Source: Wikipedia.

This makes sense to me, because pressure increases with water depth, meaning more wind energy is required to move 'heavier' water.

Albeit, I do not understand why,

The direction also shifts slightly across each subsequent layer (right in the northern hemisphere and left in the southern hemisphere). Source: Wikipedia.

My only idea is that it may have something to do with this,

The impact of the Coriolis effect is most significant with high speeds or long distances. Source.

Explained a little bit here,

Because it largely depends on how large the difference is between an object's velocity is and the ground's velocity, the effect is really only significant at high speeds (either type) or long distances (north/south especially). Source.

So the direction of water shifting slightly across each subsequent layer might have to do with the different velocities of the water layers compared to each other and the wind. Furthermore, I get why the Coriolis effect is greater over longer distances on Earth, because points on the equator are moving faster then points on the poles. However, what do these sources mean by high speeds exactly? Are they referring to the object's speed due to the Earth's rotation (pushing it in an Easterly direction) or due to the force pushing an object in a Northerly or Southerly direction for example? How do higher speeds make the Coriolis effect greater? The answers to these sub-questions will help me understand why water drifts at an angle to the wind.

Sarmiento, Jorge L. "Ocean biogeochemical dynamics." Ocean Biogeochemical Dynamics. Princeton University Press, 2013.

What part(s) of the ocean have the most sunlight hours?