In article , Sacha
writes
For swimming pools, I've seen covers that run in grooves along the pool and
are strong enough for a man to stand on but again, I think we're talking
very high costs. Your alarm sounds a better bet.

Yes there are such covers but these are for covering the pool over
winter or at night - they are quite unwieldy and not something to "pop"
over to keep it safe.

Alarms or fencing with a locked gate are obligatory in France; unlike a
pond, a small child would be unable to stand up. My late sister had an
enormous, beautiful pond and she had a grid fitted just under the
waterline so that the twins couldn't push each other into it!

--
Judith Lea