I know Florida's heat can cause misery to some lawns....but you are not doing your grass any favor by watering as much as you are.

What you are saying is.....grass needs water...the more the better.
You are drowning the roots which, once they have taken in as much as they can use, then cant take in anymore, the water sits there and rots the roots.....killing the grass above.,

I'll grant you some grasses need more tha others....and some grasses, no matter how much water you give it....will turn yellow in the fall to return to its green int he spring.
Bermuda grass, I believe is one of these.
St Augustine grass will put up with some drought during dry spells.
Try watering your lawn when the grass can take it in.

This is a fact. Too much watering causes grass roots to be stunted.....it dies when the sun's heat hits.

Too little watering causes grass roots to be stunted....it dies when the sun's heat hits.

You have to find the happy medium..

Was this new sod that was laid? If that is the case then you didn't water enough. Should have been 3-5 times a day the first couple weeks.

It went down three weeks ago, so can it be fixed? How?

It went down three weeks ago, so can it be fixed? How?

I agree with neilaz. New sod needs to be watered briefly 3x per day for the first couple weeks. Briefly means just enough to moisten the top sod and keep it alive and get the roots to penetrate into the soil below. Once that happens, then you can back off on the frequency and start watering much more deeply. Eventually you will be watering only once a week in the summer heat and every 3-4 weeks the rest of the year. But you're not there yet.