There are 2 ways from RJ-45 connector preventing water. Please see the below figure and steps.
Method 1:
Step1: Connect Cable into RJ-45 connector.
Step2: Open the Back Cover and then take the RJ-45 connector inside of the back cover.
Step3: Cover the Back Cover.
Method 2:
Step 1: Stick and bind with adhesive tape on RJ45 cable connector after connect the cable to “P+DATA OUT” port of PoE Injector.
Step2: Finish.