How to fix a water damage 3ds

Over three years ago my toddler son at the time throw his sister 3ds into a tub of water,I dried it of with a towel but I didn't submerge it into a bag of rice like everyone else suggested,when I turn it on its comes on then you hear a click n then it's off again.my question is, is it the batt or something internal n how can I fix that???????? Please help me?