Squeaky wheel

Hi All. I've developed an intermittent squeak from what I'm pretty sure is the rear offside wheel. Seems to be worse on slight left handers, sometimes goes away briefly then comes back. I think it may be linked to me backing down a slipway into water to pick my boat up. My question is. Is there anywhere to grease the wheel bearings? I'm on holiday and don't have any manuals with me and don't want to go running to a dealer if I can do it myself with a grease gun.