NOAA has published a metric chart for the area around the south and west Florida coast. http://www.maritime-executive.com/article/Coast-Survey-Publishes-New-International-Chart-for-Navigation-Between-Florida-and-Cuba--2013-03-20/
If you click on the chart numbers, you will open a viewer pane. A cartoon of the whole chart appears on the left with a draggable navigation box, and the right pane lets you zoom in and see the detail of a small area of chart. The primary difference between the metric version and the Customary: *Depth scale *Loran lines (does anyone still use Loran with GPS?) On the metric chart, the depth is in meters. The small number similar to a subscript is tenths, ie decimeters. Blue water is less than 20 m, white water is >20 m. Outside the 20 m line, the resolution seems to be 0.5 m On the Customary chart, depth is in fathoms, blue water is <10 fathoms, and shown to 1/4 fathom resolution, whole fathoms in deeper water. Bays and inshore areas are void of detail as you should switch to a higher detail coastal or inlet chart. Distances are not really marked, lat/long is used instead. Any measured length (with dividers) can be laid against the latitude scale, 1 minute of latitude = 1 nautical mile (approx). The chart is Mercator, so the scale changes (slightly) over the vertical extent of the chart. Measure any distance centered on the latitude scale near the midpoint of your run. (Note: 54 minutes of latitude is approx 100 km, or 1 degree is 111 km. These guidelines are based on equator to pole being 5400 nautical miles or 10000 km. Both are approximations as the earth is an ellipsoid and not quite that size, but are standard in Mercator navigation.)
