As a houseplant expert, I'm often asked how to water a cactus. After all, it's one of those plants that looks happy, until suddenly it's shrivelled, has yellowing fluffy patches, has become lopsided overnight, or (worst case) the top part has flopped over and no longer seems to be attached to the roots.
I've been caught out myself a few times recently, losing cacti that I assumed were pretty indestructible; I'd even repotted a cactus and thought I'd got the watering regime right, yet lost the plant shortly afterwards.
