I did a shark dive off of Maroubra, one of Sydney's many many beaches. We were dropped off shore with the dive leader and descended to the lip of a cave just off the coast. A pod (?) of grey nurse sharks essentially lived in the cave, which had a very wide openning, and so we were positioned about 10m away from the opening/overhang.
I remember the experience vivdly - the water was churned up a bit that day owing to it being very choppy. As we settled down outside the cave, we couldn't see much, but then as I focused I could make out these large, grey, nebulous shapes, swimming back and forth like they were pacing. There were 4 or 5 at the time, and they would take turns swimming to the front of the cave, somtimes coming straight towards us. they'd get maybe 5m away when they'd veer off ... unfuckingbelievable.
After diving the GBF a number of times, I find it fascinating to think that underwater animals congregate and arrange themeslves much like we do. Dive leaders know that if you go to this rocky outcrop, you'll find the neighbourhood octopus somewhere nearby, or right under this particular ledge, lives a family of crayfish.