In 2018/9, rapid assessment surveys (RAS) of 14 ‘Clusters’ of three sites, one marina/harbour site, one nearby shore and one more distant shore, were completed in the Solent, as part of a European Maritime and Fisheries Fund Project conducted by Natural England and The Marine Biological Association. That project developed a replicable survey methodology to map INNS on shores within SACs and SPAs. Comparison of this information with inventories of INNS in the associated marinas enabled assessment of the risk of colonisation of natural shores by INNS from nearby marinas. Natural England wished to undertake similar work in Devon and Cornwall involving three ‘Clusters’ of sites to seek to establish if a similar relationship could be found between the prevalence of INNS found within marinas and INNS found on intertidal areas nearby and more distant shores.