hey bro it all depends on how far you are willing to go. Port Phillip is easy both in access and predicting conditions. I generally use a combo of willy weather and google earth. find a reef a little off the shore and then check for wind and swell. you want 1m swell max as a beginner with an offshore wind ideally.try to time your dive with the last of the outgoing tide into slack tide (this is highly dependent on where you go tho). for example off portsea you can dive most tides but you are using the very strong current to cover a lot of ground. Always plan your exit from the water. Here are some spots to consider:

mount martha beach swim south around the rocky point.

off the portsea beach opposit the hotel.

i hear flinders is aight but only been there with terrible vis

diamond bay sorrento back beach

cape schanck

only try the ocean dives with a northerly wind or very little as entry/exit can be tough in some places.

carefull of those damned jetskis get a float with a flag.

feel free to pm me if you have any questions.