July & August are the two equally coldest months in Melbourne !!
For the surf, you'll be wanting at least a 3/2 sealed steamer, and probably booties (and a car to get out of Melbourne).
For flat water, if you don't fall in, you'll survive with thermals, plus boardies and T over.
(PS - you have to admit, boardies over thermals is a must !! But boardies over a wettie stirs some debate !!

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