Mog,
Indeed - which is why we did an overwater demo on the course. Flying at 20 ft over the water gains you very little except a wake - the same, of course, over dust, sand and snow...The more time you spend avoiding hitting the ground, the less time you've got to look for other threats. The time for 10-20ft is over a desert locked up by an RF SAM (whether the enemy's or, indeed, your own....).
I think the Cranwell flypast has been somewhat relegated in recent years on the FSS by a certain Typhoon incident. Most amusingly, I was on the FSS with the said pilot and his "version of events" was somewhat different to the Chain of Command's....clearly, the D Staff hadn't all been briefed as there were a few awkward shuffles when the presenter started with "let me tell you what this muppet did...." (or words to that effect...).