Water is only harmless if it is clean & neutral, plus the injection mold/steel must be clean before going into the water. This is more of lab condition that not applicable to your situation. Gasoline or diesel is not the right way to clean the plastic injection mold, it is unhealthy and unsafe. Hydraulic parts and electrical parts should be replaced straight away (the fine particle in the flood water can penetrate far more than our imagination), it is a time bomb that will down your production in China without any notice in future, not worth to take the risk. Our Chinese injection mold companies are facing the same problem. We are seeking for a proper and faster way to temporarily import the plastic injection molds into China and refurbish the injection molds. You know, due to Customs control, the main issue is time consuming.
Just get the plastic injection mold out of the water as soon as you can, send it to your injection mold maker for a complete cleaning and inspection. In case your plastic injection mold maker is too busy or also flooded, you may get in touch with us, our company in China is ready to help you getting through this difficult period.