There are times when it would be nice to press a button and become invisible. I was paddling my kayak along the river and ahead I could see a little egret: easily visible from 100 yards. At once my ambition was to paddle past without disturbing a single one of those lovely white feathers.

You can see egrets from a long way off because the white stands out. That might seem like bad design but see it from a fish’s point of view. Or not: to a fish looking up from beneath the surface at a bright sky a pure-white egret is perfectly invisible.

This one was resting up on the bank after a hard morning’s fishing. I still feel a touch of privilege when I see an egret; perhaps that dates me; they’ve been a routine part of British life for 25 years. My approach was quiet, if not quite inaudible, but as I got close – although I crossed to the far side of the river – I was altogether too visible and the bird took off with a rather weary grace, white against a blue sky. Sorry, bird, I didn’t mean to be visible.

Heading back I saw a dabchick, floating high like a bathtub duck. They look so buoyant you can’t believe they could even get their shoulders wet, but in a single instant – perhaps he had pressed a button – he vanished. Presumably he had dived beneath the surface, but there seemed to be no transition between floating high and utterly gone.

Dabchicks dive to fish and to escape, a sound strategy for both. I looked around for its reappearance, but it was as if he had never been there at all. Presumably he had surfaced among the reeds at the edge, watching me pass before taking up serious fishing again. There’s a song in Ulysses, quoted from the pantomime Turko the Terrible.

I am the boy

Who can enjoy

Invisibility!