i'd like to go snorkeling in the great barrier reef in australia and was wondering which service to use and where to get it (i am assuming i'll be able to get it from sydney?)
as low budget as possible?
You cannot access the Great Barrier Reef from Sydney. Australia is huge... it's about a 4 hour flight from Sydney to Cairns at the Northern end of the Reef. And then it's ~2 hours on a boat out to see the coral. Or 1.5 hour flight to Hamilton Island at the southern end of the Reef.
There's lots of advice on snorkelling the Reef and good operators on this thread: http://answers.worldnomads.com/questions/australia/10902/we-are-hoping-to-snorkel-the-great-barrier-reef-near-cairns-or-pot-douglas-can-you-recommend-an-excursion-for-dec about 5 years ago