As mentioned above, brushless motors rarely if ever have any issues with water or debris, at least electrically, and can even be run submerged with little issue.
The most susceptible components are the sensors (hall and temperature), and the bearings.
Since the sensors have a constant 5-volt DC supply going to them, they’re somewhat susceptible to corrosion if exposed to conductive (salty) water if they haven’t been completely waterproofed or encapsulated in conformal coating or epoxy.
The bearings are usually made of a fairly high-carbon, low-alloy steel (AISI 52100), which while extremely hard and wear-resistant, isn’t all that resistant to rust and corrosion. There are stainless, coated, and even ceramic bearings, but they’re far less common and more expensive.
As long as you make sure to dry the motor out thoroughly after it gets wet, and rinse off any potentially salty or corrosive contaminants (salted roads are awful for cars and PEVs alike), you should be fine.
A little water now and then won’t hurt them, especially if it’s fairly pure water - it’s long periods of exposure and salt that really do a number on them.