Book excerpt: The marine environment is almost ideal for the preservation of artefacts and, until relatively recently, it also provided complete protection from destruction by man. However, the aqualung has made most shallow underwater sites accessible, leading to widespread plundering. Current deep-sea bed technology now threatens deep water sites. There is a need for immediate international action to preserve the man-made environment, alongside the natural one. The enunciation of legal rules to protect the underwater cultural heritage is a complex issue, involving a matrix of interests and laws, both international and national.