This is a pretty common occurrence so don't beat yourself up over it.
Surfcasting (and actually catching fish) is a lot harder than it looks for the beginner. There are many people who've decided to take up surfcasting and been thoroughly discouraged after not catching anything.
Phill could be right there too, not all fish need deep water. One of the easier fish to catch would be kahawai and they can often be caught right in the surf, in the depth you are wading in..
Try fish baits (pilchards or anchovy) as squid is effective on some species, but its not the all round, multi purpose bait for everything.
What time of the day are you fishing?
Dawn and dusk on any tide are better than perfect tides in the middle of a hot sunny day.