I have a Hobbywing SC8 waterproof esc in myTelluride with a 4000kv Toro 550 motor and it does well. I've had it under water a few times when I didn't get the waterskip right. This esc isn't sensored though.

I think you have to use conformal coating on the board in the T8 to protect it and you would have to do the same with the Xerun esc too. Use a Dielectric grease on the sensor wire port to help there. Not sure if you are on RC Crawler or not but they have a lot of info on waterproofing electronics there.

I think I saw John Holmes from Holmes hobby say he can waterproof anything so you may want to get in touch with him on exactly what to put in there.