Royal Navy Sea Harrier FA2 lying submerged in the River Yeo after over-running the runway at RNAS Yeovilton:

Please note - these photos were not taken by me. If anyone objects to their use here, please contact me.

It happened on the 8th October 2001, when Sqn Ldr Spon Clayton over-ran runway 22. He ejected safely, but the Harrier continued on through a fence and came to rest in the River Yeo. The Environment Agency were a bit freaked out, because of the jet fuel which inevitably ended up in one of Somerset's most important rivers.

Story as told by the attending fire crew here

Also worth noting is Mr Clayton's distinctly non-Royal Navy rank of Squadron Leader. One could speculate that he was an RAF GR7 Pilot seconded to the Royal Navy. NATO classifies the rank of Squadron Leader as OF-3, which is equivalent to the Royal Navy's Lieutenant Commander. This was not his first ejection either. As a Flight Lieutenant he ejected from a Hawker Hunter T8C on the 15th February 1992 70 miles off Stornoway while carrying out exercise air raids on HMS Battleaxe. This was a FRADU Hunter, based at Yeovilton, so he obviously had a long history of flying Royal Navy jets.

I tried to find out whether it was repaired and returned to flight or not. Rather confusingly, all I can find is two different aircraft wearing the same "122" markings. One is now the Gate Guardian at RNAS Yeovilton, which does seem sensible. The other was flying as recently as March 2004, which seems less likely.
 

Edit: 18th July 2007, 12:06 am: It turns out that the "122" on the side of the aircraft just means that it belongs to 800 Squadron RN. Quite why they don't paint "800" instead of "122" I can't imagine. A picture of the same plane, as an FRS1 Sea Harrier, (before it was rebuilt as the FA2 version seen here) embarked on an unknown carrier can be seen here.

Incidentally, the story linked above mentions the "threshold of Runway 04". But in order to over-run the end of it, Sqn Ldr Clayton must have been using Runway 22 (the same runway, but the opposite direction). Runway 04/22 is the much shorter, SW-NE runway, not the main 09/27 runway where we were treated to this incredible sight at air show arrivals in June 2006.

Edit: 6th February, 2011, 20:06: I've done a bit more digging recently as loads of people link to this page. The aircraft in question is ZD614, which makes it neither the gate guardian at RNAS Yeovilton, or the FA2 flying in 2004 above. It was in fact moved from Yeovilton to RAF St. Athan at some point after the accident, then to Everett Aero in Sproughton, near Ipswich exactly a year after on 8th October 2002. UK Serials has this photo of it, taken on 19th June, 2002, at RAF St. Athan here. You can see the damage to the nose matches the last picture shown above. I've also found it here and here on 16 September, 2002 at RAF St. Athan on flickr.