James
I've used both 3M 5200 and Sikaflex and have found them to be very similar in performance (and mess created when applied).
3M 5200
Sikaflex
No 3M distributors in Australia. You can order 3M products from their website
Shop 3M
If you can't find the 3M 5200, the Sikaflex will work just as well. Just make sure to get the type that is made for below the waterline applications. They sell Sikaflex at
Whitworth's