Re: Water...OK. Just don't dive into kerosene!
Amber is usually found in water or washed ashore in the Scandinavian countries after having been in the sea for several thousand years. In other words: Water won't damage it. Neither will it damage larimar. However, beware what kind of metal your jewellery is made with. Not all that looks like silver is silver, and some of the metals should not be in water for too long.
Regards,
Susanne