Apple put an end to a historical myth surrounding mobile devices: whether or not rice is useful to save a wet cell phone. While many models are submersible, there can be issues with charging.
The main danger lies in the charger area, since charging an iPhone that is still wet can cause permanent damage. The iPhone should be left in a dry, airy area for a day. It will probably take 24 hours to dry completely, although during this period you can test if it charges well.