MarkSetBot chargers delivered after January 2021 are waterproof. If your chargers do not look like the photo below, they are waterproof.
For chargers delivered before January 2021:
Amazon has a box that is perfect for waterproofing 1 to 4 chargers made by SOCKiTBox
The medium box can hold 1 - 2 chargers. The large box can hold 1 to 4 chargers. The small box is too small for a single charger.
You can use this 4 way splitter to power your chargers
Here are pictures of the set-up: