I typically wear a bathing suit bottom or swim skirt but this year decided to try the 1/2 sleeve top with board shorts. I am 5'3" and I typically wear a M. I am 42 year old mother of 2 toddlers who used to be sporty in the good old days but not so much now - I say this because I was hesitant to purchase the shorts thinking they would only look good on a teen/twenty something surfer girl. I was wrong (they would look good on that girl but also looked good on me)!
Fit - true to size and flattering. I ordered a L (in the short length) and M (in short and med length) and opted for the M. The L was way too big. The M fit the same in both lengths.
Length - great for a more sporting around but a bit long for swim suit substitute. The short length would work great for a swim suit.
I bought both the short and med length and love both (disclaimer - I have not worn them in the water yet).