Hi Alyce, in Byron Bay in July the average daily temperature is 19 degrees and the ocean water temperature will be about 20 degrees. If you don’t mind cool water or have a light wetsuit I recommend taking a pair of googles and a snorkel and looking at different types of fish. On the main beach (Clarkes Beach) just north of the Captain Cook Lookout there are rocks on the shore that mean that a unique kind of lagoon is carved out at that spot. Last time I was there, (at the right point of the tide) I saw about eight different types of fish swimming in that area – from colourful tropical fish to large flathead and small stingrays. You can just wade in right from the beach. I strongly doubt there will be any jellyfish around to worry about but keep an eye out on the shore before you go in. If you are more adventurous you might join a snorkelling tour to the Julian Rocks park which is about three kilometres off the coast. They supply wetsuits. The walk up to the Lighthouse Rd is a must. You will also be there during the whale watching season so some binoculars might be a good idea. Have a great holiday - Byron is a unique place.