As has been said, I don't really understand the excitement about sockets under sinks - or,to put it the other way around, why there is not similar excitement about electrical accessories in all sorts of other places.It's permitted but IMO undesirable. I'd consider swapping it for a weatherproof "outdoor" one with the cable entering from underneath and a lid that will shut with a plug in it.
I think I've always had sockets and/or FCUs and/or JBs /whatever under, or nearly under, kitchen sinks, and in very close proximity to all sorts of water and waste plumbing, but don't recall any case of a resultant problem. On the other hand, over the decades I have had a fair number of instances of accessories in other locations 'filling up with water (due to plumbing, CH or roof leaks - and even an overflowing bath on one occasions ) - including ceiling roses/light fittings, sockets, FCUs, JBs light switches and even CUs. Do you think I should have installed weather-resistant "outdoor" accessories throughout my house?
Kind Regards, John