Brakes Grab on 1998 Dodge Durango

What causes teh brakes to "grab" when they are wet?

Asked by for the 1998 Dodge Durango
Brakes will grab after being wet momentarely, if they continue when not wet u are leaking either axle fluid or brake fluid from wheel cylinder and will need to b ficed or will grab horribly and pads will have to b replaced because of contamination.