In the presence of an electrolyte the gold causes any LESSER metal to be corroded at an accelerated rate.
Hence gold connectors should only used with gold and tin to tin plug in cards are far more reliable than gold to tin.
So the USB socket is fine and obviously can't be coated or it wouldn't work with the plug. In any conductive liquid the gold causes accelerated corrosion of the aluminium and tin.
Stainless steel bolts on an aluminium structure can cause the aluminium to rot, for a similar reason, so historically the stainless steel was cadmium plated, or the aluminium had an epoxy coating.
Any bathwater or saltwater immersion will result in increased rate of corrosion of any exposed reactive metals BECAUSE the gold is there.
You can test this at home with and wiithout a wedding ring and various metal in regular salt solution, vinegar, baking soda water, coca-cola (has phosphoric acid) and dissolved bath salts.
You can even make a primitive battery with gold , lemon juice and zinc. The gold isn't harmed at all! It might get a bit zinc plated, but it will polish off.
https://blog.samtec.com/post/dissimi...ng-connectors/
"Improper use of aluminum in contact with stainless steel had caused rapid corrosion in the presence of salt water"
https://en.wikipedia.org/wiki/Galvanic_corrosion
The best waterproofing concept is keeping the liquid out. So professional gear designed for immersion uses a neoprene sealing ring compressed slightly by a precision screw on cover, or a cover held by screws exterior to the sealed contents with an elastomer seal between the two halves.
The original H2O had a push on cover with sealing ring, a membrane at the power button and double sided single piece waterproof sticky tape for the main cover. It wasn't very reliable and the main cover could easily get slightly peeled. The small cover would wear.
The Libra H2O's HZO system is even cheaper and because dust, grit dirt and liquid can get inside, especially via the front buttons and the USB socket, it's only for accidental dunking. The back can easily be popped off with a thumbnail starting at the corner diagonal from the power button.
It's a lovely eReader but the case and waterproofing could have been better. It's a really cheap design compared to screen and electronics.