Thanks davidships & mikedavies43. I've always been fascinated by Guard vessels.

After the 1988 Piper Alpha disaster I think the opinion was that converted trawlers were no longer adequate and the trend began towards using converted oil rig supply vessels (usually the smaller, older ones) and then purpose-built standby vessels - in addition, many supply vessels now seem to have a "Rescue Zone" marked on a hull area with lower freeboard.

Like CELITA, many of the former trawlers seem to have ended up back in the fishing industry.

In the UK at least the growth of North Sea oil brought a need for Standby Safety Vessels (stationed at rigs etc to provide recovery services in case of accidents) and Guard vessels (mobile keep-away warnings). This was just at the same time as a major decline on the fishing industry and the vessel owners were only too keen to charter their surplus vessels for these services, for both of which the vessels were eminently suitable - small, all-weather stable vessels. The oil companies paid good money. Later SSVs tended to be based on OSVs, and now often specialised designs. For guard duties almost anything sea-frindly that is big enough to make a good radar target and has a crew that will actually keep watch would suffice.

What's the history of Guard vessels? Were ex-trawlers always used as Guard vessels?