Navionics has good coverage inshore and offshore in the Gulf. Spot soundings with Nautical Charts and HD depth contours with Sonar Charts.
The actual maps can be viewed on the Navionics website's Web App. Have to zoom in to the .3 mile scale to see the 1' contours
Humminbird, Lowrance, and Raymarine have sonar/GPS units that read Navionics digital mapping.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, 360, RC-1