Our house is on a deep canal in Avon. Over the years, we've caught everything that swims in that canal. But mostly it's slow fishing better suited to beer drinking than fish catching.
Some canals are too shallow or mucky to fish. In a fishable canal, you'll find:
1) Schools of small striped mullet and menhaden. They're filter feeders, you can't catch them on a hook. But if you can throw a cast net, they're great bait for sound or surf.
2) Bait thieves - pigfish, pinfish, lizard fish, etc. I kayak fished for speckled trout in the sound behind Avon last week and was run off by 6" lizard fish.
3) Spot and croaker. If you're not overwhelmed by the thieves, bottom fish using small hooks with bits of blood worm, shrimp or fishbites.
Fishing the sound is usually more productive than the canals. The trick is to find deeper water. Much of what you see from shore is only a couple of feet deep. Use Google maps satellite view to locate the deeper spots.
If you wade fish, wear water shoes to protect your toes from crabs and shuffle your feet to scare off the rays. There can be lots of small rays cruising the shallows.
The best bet for game fishing is to fish the deeper spots and grass beds from a kayak or small boat for speckled trout and puppy drum. Over the grass beds, try popping corks with 1/8 ounce lead head jigs or hooks baited with shrimp or fishbites. The popping cork will keep your lure or bait out of the eel grass. In deeper spots, try a lead head jig or a mirrolure. Or bait on a top and bottom rig.
Consider booking a kayak or small boat charter early in your trip. These guys know the best spots. Once you've seen where they fish, you can return on your own later.