The RNLI Inshore Hovercraft has been developed to improve search & rescue capabilities in specific areas where conventional SAR techniques are difficult, slow and hazardous. Typically these are large areas of tidal mudflats or sand where the surface is too soft to allow access to land vehicles but too shallow for boats. Each year these areas experience a number of incidents where individuals or groups of people find themselves caught by the rising tide or trapped in quicksand or soft mud. Unless help is provided rapidly, this situation can result in tragedy.

Until now the only method of rapid access to these areas has been by helicopter. Surface access has been limited to walking using mud mats and crawling boards. The main advantage of having a hovercraft available in these areas is its ability to rapidly search large areas of mud, sand and shallow water. Once the casualty has been located, the hovercraft can settle alongside, providing a large, stable platform to conduct the rescue. The craft carries specialised mud-rescue equipment to release a trapped casualty as well as basic First Aid equipment. The IRH can be kept mounted on its own transporter which will allow it to be rapidly dispatched to any area of concern.

It is recognised that a small hovercraft has relatively limited sea-keeping abilities, being restricted to a wave height of just two feet, and a wind strength of 25 knots. However, it is envisaged that should the IRH be required to cross open areas of navigable water, the co-located ILB could be launched to assist.

The hovercraft chosen by the RNLI is based upon the Griffon 450 TD produced by the Griffon Hovercraft Ltd. After extensive trials by the RNLI and Griffon, significant changes were made to the original design, resulting in the Griffon 470 SAR model. These changes include stretching the original design, removing part of the side deck and adding two inflatable sponsons, similar to those used on RIBs. These provide additional buoyancy, stability and offer a soft edge for survivor recovery. The sponsons can be deflated, reducing the overall width sufficiently to allow the craft to be transported by road. The craft's skirt height was also increased to give an increase in ride height to improve sea-keeping.