I know this is a late reply, however I remember while antifouling my boat next to the Shamrock Quay office a couple of yobs where trying to steal a bike behind me. I only realised when I heard a noise behind me and the Marina staff had caught one of them. The police turned up and so on - so it might be worth checking with police & marina office (probably stating the obvious).

This was a few years ago 2003 ish prehaps, but these yobs apparently do the circuit from hythe to shamrock etc.

Regards,
Richard.