[wang_li]

The horizon at sea level is about 3 miles. The strait of Hormuz is 35+ miles wide. Any mechanism used to get around this would be detectable and could be attacked with relatively inexpensive ordinance.

[cyberax]

About 20 meter elevation would be needed to cover the navigable part of the strait. So, a couple of tall ladders?

[don_esteban]

Look at the map. They have mountains. Not much rain/fog in that area to block the sight lines. Maybe haze.