I wouldn't wait for any other responses, Deemar got it bang on and I agree with overtauk's addition about the sink due to increased "apparent" gravity.
As far as mass increase goes, rest mass is the lowest you can measure of an object, which occurs when it is not moving relative to you. The faster the object moves, the greater the mass you will measure (negligible until very close to the speed of light). The rest is beyond the scope of this forum. There are many good books on special relativity.
Matthew.