When I was a wee kid growing up on my folks’ farm in East Anglia, it was a common sight, in the 1970s and 80s, to see RAF Jaguar and Tornado jet aircraft practicing very low flying over the flat (ish) fields of that part of the UK. Typically, a Jag could fly no more than 100 ft off the deck, so low in fact that you could see all the markings on the side of the aircraft, what sort of stuff it was carrying, etc. The idea was to get under the opposition’s radar. These aircraft were practicing the sort of flying that would be needed against the-then Warsaw Pact ground forces of the time. (The Jaguar was a very effective strike aircraft).
But nothing, absolutely nothing, compares with flying as low as this. Ye gods!