It's been discussed on other forums, it was one that sank in 1952 ish (Feb?) and on being raised a day or so later, caught fire from (it is believed) the flame/smoke flares. Hence nothing was able to be removed.
The RNLI Lifeboat is using the Sunderland mooring. It hasn't been dived as there are specific restrictions to diving below lifeboats. I'm sure others will come up with the serial, something like P1188 or similar...
Edit: Have now found the other thread:
Sunderland GR5 - PP118 - Key Publishing Ltd Aviation Forums