Synchronous measurements of aerosol extinction α(λ) in marine environment show an increase of the sea salt aerosol concentration at a growing wind speed. At the same time, the opposite effect is observed in coastal conditions. There is a decrease of α(λ) at increasing wind speed in the sea and coastal surface layers. This means that the change in the scattering value can be described (when ignoring the effects of the second order at high wind speeds) by a source modulated by the changing wind speed and direction. The hypothesis is proposed, which is proved by results of calculations by the author's aerosol model allowing an explanation of this visible contradiction. It is offered to use the fetch for the explanation. It is shown, that at small fetch (coastal conditions) and increasing wind speed, there is a decrease of aerosol extinction α(λ) in the spectral wavelength range Δλ = 0.2-12 μm, and at big fetch (marine condition) an increase of α(λ) occurs at an increasing wind speed.