I read somewhere that the advice given to competition swimmers is to wear your hydrasuit two sizes 'too small' so you'd want a 36". That's what I do and it seems a good rule of thumb.
I tried size 36 a couple of times, but decided to stick to 38 (like my wife) My daughter's got size 36 (the latest version of Speedo water-polo hydrasuit with high cuts), so it's a bit ... too small.