I think you've pretty much got it. What I'm going to write, since this is a nontechnical audience, is that frankly, ground effect is a complex, difficult-to-explain phenomenon best left to textbooks, but suffice it to say that an airplane flying very close to water or level ground such as a runway experiences less induced drag. The downwash angle is also reduced, and this rotates the lift vector forward, thus allowing an aircraft to stay aloft using less power and less fuel. Or, in the case of ekranoplans, carrying more weight than they could otherwise lift outside of ground effect.