Ground Effect

It's flat-calm April weather. Drizzly one moment, blazing sunshine the next.

The birds are enjoying it. Swallows swooping perilously close to the water, catching ever-more-abundant flies; loose flocks of Meadow Pipits beetling round the lawn and the damp soil; a robber-masked Wheatear bouncing between the rocks.

And of course there's the Grey Heron. When the sea is as calm as this it skims in low over the water and makes lazy, elegant use of the "ground effect". Gliding low like this alters the airflow around its huge wings, reducing drag. Curiously, "ground effect" isn't much use over land as there are usually too many obstacles to get low enough.

Humans, particularly Russian humans, have made interesting use of the "ground effect" in "ground effect vehicles" such as the Ekranoplan, nicknamed "The Caspian Sea Monster".

I wonder if it would fit in the bay? Might startle the Heron.