Thought it might be fun for you to see the charts we use and our routes and waypoints around Southern Belize this past month. I've used screen shots to give you an idea. You can enlarge each map to get a better view.
The blue lines are our routes through and around the cays. The yellow names are waypoints (latitude and longitude points on the map that we sail to). On the chart the colors are confusing at first. The green blue near shores is shallower and the white is very deep. Luckily the depths are marked.
Belize has a safe, reef free, inner channel between the shoreline and the first line of cays (blue area near shore). Its 40-60ft deep so you can sail here without keeping a bow lookout for coral heads. There is also a very deep mid-channel named Victoria Channel that averages 60 - 100 ft from the mid point of Belize most of the way South (see the white area on the charts). Victoria Channel winds its way through the middle cays which are often mangrove cays though some are part mangrove and part sand/palm trees. Victoria Channel is mostly free of coral heads but you do still have to keep a sharp lookout as there are shallow patches and areas of coral that extend from the seafloor and these need to be avoided. Once East of Victoria Channel you are headed towards the reef and it is much shallower 5 - 15 ft with coral heads and reef patches reaching to the surface. Coral and reef patches are marked on the chart as a red "+" but this denotes many coral heads and reef patches so a red + means "beware of this entire area. The cays here are sand and palm trees. Outside of the reef is the Caribbean Sea and depths quickly reach thousands of feet except for the atolls.
Our route from Placencia SE to Ranguana Cay then NE along the outer cays to Silk Cay, Little Water and Rendezvous Cays. Little Water was very difficult as the chart was off.
After Rendezvous and N Long Coco we went back to Placencia. When we left the next time our track was N to Sopodilla Lagoon to Sanctuary Belize (we didn't run over the land but stayed in the Inner Channel). Then we went E to Whippari, S Long Coco, Hatchet, then out the Queen Cay Cut to Glover's and back in to South Water Cay before coming on to Belize City.
This is our entry from Victoria Channel to the anchorage at Rendezvous Cay. We had to very carefully eyeball our way through the coral between Long Coco Cay and Rendezvous. There is a reef near Long Coco which isn't shown on the chart but clearly shows up as you approach.
Polarized sunglasses are a must and the general rule is move only when the sun is high in the sky. Go East between 11am and 2pm, West early morning until about 1pm. If you can do that and remember your liquor bottles you'll be OK. Sky Vodka: 50+ feet, Tanqueray and what you imagine it looks like if it where more blue: 25 ft or so. Bombay: about 15ft. Watch out for anything that looks like Amsterdam Gin and definitely remember how bad you feel after a Cuervo Tequilla night (coral heads coming to the surface!!)
These are Navionic Charts from MacEnc on our IMac.
Of course, you wouldn't want to cruise Belize without Captain Freya Rauscher's Guide to Belize, Mexico and the Rio Dulce.