With the water displacement and (double O-ringed) sealed doors and rear gate, it would not take much to make the CyberTruck amphibious despite the weight, as Elon said, the electrics are already insulated/water sealed... and with the (limited?) pass through for quick excursion or perhaps a...
Update June 25, 2020
Elon once again teases that the Cybertruck will be able to float.
Original post April 20, 2020
Per Elon Musk tonight, the Cybertruck will be able to wade and even "float for a while."