As joelage said flinders pier is the best spot for seadragons. High tide is the best time as it can be difficult to get in/out at low tide. They are normally found under the pier or in the grass on the left. There is no dive shop at flinders,best spot to get gear is Rye.
There is a dive shop opposite Rye pier, which is handy to get yourself sorted out in the water before heading to flinders.
On a good day Rye pier is great spot to dive all day, Rays, squid, octopus and if you time it right the spider crabs will there be in there thousands
Portsea pier can be hit or miss finding seadragons and the surge can be annoying if you want to photograph them but there is a dive shop at Portsea. Dive Vic runs boats out of Portsea but have a very limited schedule during the week.
Water is getting cold.
A car is needed to get to anything worthwhile. Flinders/Rye/Portsea are all about a 90 minute drive. Public transport sucks to get down there about a two day trip via tram train and then bus from St kilda.
Also Blairgowrie pier is also a great dive spot if you are there before they start ripping up the marina, after that it will be anyone's guess if it will be worth diving
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