There is products around like the Aircare Firesock Battery Risk Management System that will contain a phone, tablet, laptop. Larger aircraft generally have a stainless bin in the toilet and bottled water where a device can be placed and soaked in water.
Possibly due to some translation issues, the local regulator has us trained only to immerse in water after a cooling period of 10-25 minutes. The original guidance is supposed to be FAA, is there a valid reason behind such delay?