From a kayak-forum:

The following is a copy of a post on an environmental network in Cornwall. I am not involved, just passing on a message.

Hi Guys. Just came across two blokes who had kayaked to Gulland Rock off Padstow and climbed to the top to place a 'geo cache'. They had caused total havoc amongst the bird life presumably scaring birds off the nest/chicks giving the Gulls easy pickings. I shouted over to them and they came down and explained what they were doing. I have just looked up this 'geo cache' thing and can see it is going to be a big problem. Once it is there it is to encourage the others to all visit this 'cache'. I called the coastguard but they seemed like they did not care but I believe (and correct me if I am wrong) that it is illegal to disturb nesting birds. This needs urgently looking at.

Cheers all
I don't know the area, but maybe someone can check whether this island is a protected area and that is no chance that a cache will be publish there.