Rigid Inflatable Boat or Rigid Hull Inflatable Boat -- the choice is yours!
Either way it's not very helpful as people immediately think of a dinghy or yacht tender, and are very surpised when a ten metre 600hp beast hoves into view . . .
RIB seems to be used much more than RHIB which only seems to be in common usage in the US.
Neither is wrong. I prefer RIB