G'day
Cat....... best bet is a bost, but the bank can produce.
What is your location?
Estuary or bay, all depending on their movements.
Depth from 1/2 to 10 M, again, pending tides and movements..
A cast net will suffice, an 8' net is a good start for a beginner and a 12' if you're happy throwing one that sized for the more experienced... I find a 10' comfortable but don't have a worry with the 12.
Just look for the tinnies with the yellow raincoats and you will find the prawns.
For seq, they're still a little while away yet.
Dave