Grab your snorkel and head down to the inlet at Duranbah beach. The pristine water and abundant fish life ( dolphins and turtles regularly spotted!) make this some of the best snorkelling on the Tweed Coast. Start off in the calm waters of the bay, then turn right and drift down along the seaway wall, heading towards Coolangatta / Twin Towns Resort. This is best done on the end of the incoming tide, that way you can drift down and back as the tide changes. It is recommended to check local tide times to ensure best conditions and safety.
There are plenty of dive retailers in Coolangatta / Tweed Heads if you need to hire gear, or just to give you some more local knowledge of the area. Scuba diving is also very popular in the river. If the water isn't your style, there is plenty of grassland and shady trees to set up under and read a book or have a picnic.