These kind of waves do, but not all gravitational waves do. (You can think of the class these are as "normal", smooth waves.) Sufficiently "foamy" ones should

These kind of waves do, but not all gravitational waves do. (You can think of the class these are as "normal", smooth waves.) Sufficiently "foamy" ones should act like waves passing through material and cause interference based losses while sufficiently strange waves will travel faster than light, a la the hypothetical warp drive using negative mass.