Decko Gecko Hawaii is simple enough Aussie surf brand....prob easy to find on eBay.
The others are tough.
Who is that wearing them?
Jimmy J
(Please note: Legit checks I do in this forum should not be considered 100% conclusive; I'm simply giving a gut reaction based on the limited information provided.)
The second one looks like a cow skull/longhorn, it could be a Texas tourist tee. The third looks like "world one (chance, channel, change?)" if I were you I would search under Greenpeace, Discovery Channel, or something like that.