A lot of anchoring is done on reef and a different anchor to what you use in estuaries and rivers with sandy or muddy bottoms is required.
This video has info from Dave Oelrichs from Maritime Safety Qld on using a reef anchor on shallow inshore reefs.
Also worth looking at in the Boating Vault is the video on anchoring in deep water on offshore reefs using a float system.
Another safety tip from Boat and Jetski Licence Noosa Sunshine Coast, servicing areas including Caloundra and Maroochydore right through to Gympie.