Always useful to read - learn by other's mistakes.
They are lucky the RIB was an Ocean Dynamics with an aluminium hull and jet drive. The boat hit a rock at about 18kts - the skipper having just slowed as he sensed something wasn't right. He hit his head on the wiper motor and was concussed - other crew members bruised.
The main finding was he relied too much on the GPS - it was dark and no visual references. also he didn't use his radar for extra conformation.
To sum up - watch where you are going!!!