Oh yes Pete (Flanker), I forgot to mention.
A SIB is a Soft Inflatable Boat. This means that it can be deflated and rolled up for storage and transportation. A RIB or more technically a RHIB can not be rolled up for storage unless it has fallen off your trailer whilst you were towing it at 60 mph!
SIBs are used by 'Special Forces' as they can pack them inside submarines prior to missions.
Did I ever tell the forum about the time I jumped from a helicopter from 2,000 feet, at night, with no parachute, into the sea just off the coast of a rogue Gulf state (sorry can't tell you which one) with just my SIB under my arm and my knife between my teeth?
You try doing THAT with a RIB!
Keith (you should have seen the resulting tsunami) Hart