If the shield is in the offhand, entering water with the shield prevents it from functioning properly until removed from the offhand and added again.
Environment
Windows 10, Java Version 8 (update 221)
If the shield is in the offhand, entering water with the shield prevents it from functioning properly until removed from the offhand and added again.
Windows 10, Java Version 8 (update 221)
Sounds like MC-171484