How waterproof are eBikes?

[Flowrider]

I don't know too much about eBikes, however, we have riders in our group who are just starting out on them.

In the group, there has been some confusion about just how waterproof they are.

Rain is fine, they say, even if you get caught in heavy rain.

What about puddles, deepish ones, and streams?

Can you submerge your crankset and bottom bracket area?

Any advice would be great