Thank you for all your replies. It never occurred to me that it might be (helicopter) observers trying to navigate to ships. In this case, would said observers under training be trying to find an actual ship, or just hit a certain lat/long? Or is it a more basic / fundamental level than that?
Lj101, yes that's the NOTAM. Thanks for that
For all that remain interested, the link was to SUP 002/2013.
If any of the students happen to be reading this, good luck! I find navigating over land tricky enough, never mind the sea!
Thanks again for taking the time to reply.
Jon.