You can fly fish for bass and sea trout yes, it's quite common at low tide on estuaries however it's incredibly specialist and relies on local knowledge, wading around at low tide is exceptionally dangerous, you can get stuck in sand or cut off, it;'s something I'd only do with someone experienced.
Why not try a local stocked trout fishery so you get used to the rod and line before you venture out into the wild, you're bound to catch something and there will be plenty of advice from people.
Loads of videos on youtube about beginners fly fishing that are worth watching
I like fly fishing, if you can't carry all your kit in a messenger type bag and in the vest you are carrying too much, simples.