Hey All, I had a teachiing business, for a while, had a lift and 2 Chinese boards. I sold the lift, it was ok, and eventually the chinese boards had some issues. mostly electrical, as the battery connectors sucked, I tried a few and am stiill doing it, but eventually the motors froze. so I am starting from board scratch. Adding new esc’s remotes motor65161s and masts. first set is flipsky 75300/65161/fx3 combo. deciding on a mast and some factors like a water proof esc etc. bang away my new friends.
Welcome
Not sure if there is a question in your post 
You do mention a Flipsky 75300 which is watercooled and they rate it IP67 that seems to solve your search for waterproof ESC
I’m not so sure about how “waterproof” they can make these. Yes they are potted but the wire connections are still exposed so…… imo more “water resistant”.
it doesn’t look water proof to me in any way