No you're right there is no legislation I'm aware of regarding age, Ive seen 10 year olds using them here honestly! There is a local police jet ski about but it has to cover the whole of north wales so its not very effective. Our local beach has a boat lane so that there is a specific place for powered boats to launch and to be fair it is well used but there are a good few (always jet skiers) who insist on running parralel with the beach in shallow water where children are swimming

Spaniard, Im sure there is some regulation, pick up a copy of the seaway code or whatever its called these days, I must admit its been a while since I saw one but then we dont have a boat!