I read somewhere that there are not good places to swim. Is that true? ...Lots of weeds?
CollyK was spot on about water traffic, please do not wander past the end of your dock, a good rule of thumb is to stay inside the dock length. Think of the inner reef is a roadway for the Caye. So dont play in the street.
Most of the shoreline along the reef side of Ambergris Caye has beds of turtle grass that begin within a few feet of the water's edge and go out many tens of yards before it thins out and the sand bottom begins. Elbert might wade in on this, but I've often wondered if the depth of water dictates where turtle grass stops (I'll have to include a plumbline next time i'm out on our 'yak).
Its not tall but it definitely is thick enough in terms of coverage to make wading (for some) unpleasant since it does not meet many peoples' criteria of needing to be a pure coral sand bottom before its "acceptable". As I wade and sight fish alot its no big deal, you can get used to it. I simply shuffle along slowly so as to not tear it up as I pass.
As others have said there are plenty of opportunities to snorkel from docks and a few artificially cleared areas to suit your needs. You just may have to explore a little and follow up on some of the suggestions made here. Our dock is 350' and we have a palapa toward the end beyond the grass beds. The snorkeling around the dock, pilings, and a few close in coral heads adjacent the dock make for excellent adventure.
While wading anywhere whether in sand or turtle grass, you'll want to employ the "flats shuffle" and slide your feet along the bottom one in front of the other instead of picking them up and planting them down. The inner reef area, grass beds and sandy areas, are home to a good population of our local rays. In the unlilkely event you were to be walking an interception path toward a covered ray your shuffling feet are more apt to touch the wingtips/sides of the covered ray and cause him to skitter off leaving you both startled but unharmed. When you step directly on the ray that causes them to reflexively whip their tails defensively and of course increase the chance of injury. Again these kinds of encounters are not commonplace but its simply a piece of advice as a flats fisherman I thought I'd pass along.
The turtle grass in my opinion is an excellent bio indicator of ecosystem health. Nice thick healthy beds means healthy sealife. It's a big part of the inner reef ecostyem of the Caye and one of the reasons we have such fabulous sealife for you to enjoy.