Your bike will aquaplane if you ride too fast over a very wet stretch of road. The tyres can’t cut down to the road surface, so they simply ‘plane’ over the water like a stone skimmed across a lake. In these circumstances, you have virtually no grip whatsoever. Not nice.
The more water on the road, the greater the risk of aquaplaning. One giveaway is water running across the road surface. Sometimes deep puddles can be hard to spot but they are just as bad. Best to assume any puddle could be a problem.
If you do hit water and sense your front tyre isn’t in contact with the road, NEVER touch the brakes. The gyroscopic force from your wheels is helping you stay upright. Touch the brakes and you stop the wheel - see the problem?
Keep your front wheel pointing straight, ease the throttle off very gently and lean forward to load up the front tyre, so it pushes onto the road.
If you absolutely have to cross a flooded stretch, dismount and test the depth. The crown of the road is likely shallowest. Ride through slowly in first gear ensuring the tyres contact the surface.
Slip the clutch and use some revs if needed, so you don’t stall or let water get into the silencer.
Once out, ride with the brakes on gently for a short distance till they’re dried off.