Floating lawn, St. Augustine grass
The gentleman that treats our St. Augustine lawn called it floating lawn, The lawn doesn't seem to be attached to the soil. What causes this and what can I do about it?
I would talk to your local extension service to find out the exact cause, because it can have several. Usually fungal but it could be due to dry compacted soil as well. This link will take you to a page that you can find the closest extension service to you: https://www.gardeningknowhow.com/extension-search/
This website is dedicated to find issues similar to yours: http://neilsperry.com/2008/04/identifying-issues-of-st-augustine-lawn-management/