Sussex Marine Life was written in 1998 while Robert Irving was co-ordinator of the Sussex Seasearch Project, which ran from 1992 to 2001. (Note that Sussex Seasearch still continues under the auspices of the Marine Conservation Society, with further information being available here).
Seasearch encourages sports divers to record what they see on their dives, both habitat and species information. Recorders attend training courses, starting at the Observer level and progressing through to Surveyor level. At the time of the Sussex Seasearch Project, only a handful of species found off the Sussex coast featured in any of the GB-wide identification books on marine life available. Hence the need for a Guide that could not only increase the accuracy of what volunteer divers were recording but also improve their own knowledge of marine life. The 180+ species featured are not confined to just the Sussex coast (SE England), but range along much of the English Channel.