Thin, reddish, lines. It can be just one, or .orr often a few roughly parallel or offset a bit. The lines will be perpendicular to where your skin is being most stretched.
I've put on so quickly that I have quite a few stretch marks... I don't like them ( I know others might)... it is very hard for me to go to the pool without a shirt on. It is the reason I will probably never post a topless pic here. I really hope they fade at some point!
