Read the bottom.
Then cast.
Turn on Depth Contours and the water fills in, shallow to deep, in twelve bands with a line on every edge. The drop-off, the channel and the hole are there before you leave the dock.
Depth Contours is a free map layer in Cobia, the fishing app. It shades the water in twelve depth bands, from the 0 to 2 foot shoreline out past 60 feet, draws a contour line on every band edge and labels the main depths. It's built from NOAA's BlueTopo survey data, with NOAA's coastal relief models filling the strip along the beach.
Key facts
- Bands
- Twelve. Two-foot steps to 10 feet, then 14, 18, 24, 30, 40, 60 and deeper.
- Contour lines
- One on every band edge, and more of them the closer you zoom.
- Labels
- 4, 8, 14, 24, 40 and 60 feet and the deep steps past them, along the lines when you zoom in.
- Data
- NOAA BlueTopo surveys, with NOAA coastal relief models along the beach.
- Where
- Surveyed coastal water, the Great Lakes, Alaska, Hawaii and Puerto Rico.
- Price
- Free on iPhone and Android, like every map layer.
Tightest where you actually fish
Most inshore fishing happens in less than 30 feet of water, so that's where the steps are small. Every two feet to 10, then 14, 18, 24 and 30. Past that the bands open up to 40, 60 and deeper, and the color runs from near white at the shoreline to near black offshore.
Drawn to show the idea. A line on the map means the bottom just crossed a band edge, so lines bunched together mean the bottom is dropping fast.
Fewer lines far out, every line up close
Zoomed out, the chart keeps the major lines so a whole bay still reads. Zoom in and every band edge gets its line, and the depth labels ride along them. The lines get a touch heavier as you get closer, so the chart still holds up over a single dock.
- Labels on the depths you anchor on, 4, 8, 14, 24, 40 and 60 feet and the deep steps past them, not on every line.
- Same edges everywhere. The shading, the lines and the labels all break at the same depths.
Zoomed in on the inlet mouth. Every band edge has its line, with labels on the main depths.
Where the edge meets the grass
Depth runs under everything else. Turn on Habitat and Structure with it, and the places worth a cast stand out: a grass line on the lip of a channel, a drop-off off the end of a jetty, a wreck in 40 feet.
- Structure draws drop-offs, channel edges, jetties, docks, bridges and wrecks. It covers Florida today.
- Habitat adds seagrass and oyster from FWC surveys. Also Florida.
- Strike Zones reads the same depth to score where fish should be holding.
Survey data, not a guess
The chart is built from NOAA's BlueTopo, the national bathymetry compiled from hydrographic surveys. Survey boats can't run the surf line, so NOAA's coastal relief models fill that strip along the beach. Where there's no survey, the layer stays empty and the switch says so.
It's for reading structure and planning where to fish. Navigate by your charts and your sounder.
The same switch on surveyed water, and on water with no survey yet.
Questions about depth contours
Where does Cobia's depth data come from?
From NOAA's BlueTopo, the national bathymetry built from hydrographic surveys, with NOAA's coastal relief models filling the shallow strip along the beach that survey boats can't reach.
Which waters have depth contours?
Surveyed coastal water along the Atlantic and the Gulf, the Great Lakes, Alaska, Hawaii and Puerto Rico. The Pacific coast of the lower 48 isn't drawn yet, and most inland lakes have no NOAA survey. Where there's no data, the layer reads Coming soon to this area instead of making up a bottom.
Can I navigate by it?
No. It's built for reading structure and planning where to fish. Use official charts and your own sounder to navigate.
Why do lines disappear when I zoom out?
Far out, the chart keeps only the major lines so the picture stays readable. Zoom in and every band edge gets its line, with depth labels along them.
Do depth contours cost anything?
No. Depth Contours is free in Cobia on iPhone and Android, like every other map layer.
Know the bottom
before the bite.
Download Cobia, open the Map tab and switch on Depth Contours.
