My 3ds fell in to water and does not function properly

daniel, the very first thing you want to do is to disassemble your 3DS. Use these guides for that. Then clean every part, do not forget the connectors and cables, with a high grade isopropyl alcohol and a soft brush. Look for any missing, burned, charred looking components. Once it is properly cleaned, replace the battery, reassemble and re-evaluate. Water damage is one of the toughest repairs since you can never be sure which component has failed. The longer you leave it, the greater the chance of corrosion failure. Hope this helps, good luck