Spongy grass
 

Why does it feel so funny walking on the grass? Im from CT

St. Augustine grass is like a form of crabgrass in my opinion. Grows and spreads with runners and is very thick.

Up North our grass is grown in top soil that provides a firm footing. Florida grass is grown in a much more sandy soil. Reminds me of walking on the beach!

There are grasses that thrive in warm climates and grasses that thrive in cooler climates. We have warm climate grasses in Florida. Blue grass, fescues and bent grass are predominant up north. Those grasses would not survive in this part of the country.

The golf courses down are primarily Bermuda grass which requires a lot of maintenance. Bermuda goes dormant in the winter so they over seed with annual rye grass. The rye grass dies when the weather changes and does not come back.

Unless we want to get into the maintenance necessary for Bermuda, we can choose from St Augustine Bent, Zoysia and Bahia. None of those are anything like northern grasses.

Thanks everyone for your comments

The best grass in Florida is centipede. Low fertilizer and water needs. Highly resistant to FL pests. Grows so slow you can mow it 1 or 2 times a year. In winter it gets a bit of a burgundy tint. Never seen it turn brown south of Gainesville.

Most of your spongy feeling lawns have been in a few years and the inch of peat that came with it has gone, leaving the runners sitting up on an inch of exposed root. If you can get your finger under the runners, this is your lawn.
This leaves your lawn in a bad place as far as losing moisture and easy prey to root loving pests.
Add an inch of top soil.

Because what you have in Connecticut is real grass. What grows here is something that sorta looks like grass but is really some exotic tropical stuff that is only distantly related to real grass. Real grass will not grow here.

Exactly!!!! That's also why we carry sand on golf cart, so we can fill divot. Up north, we would replace divot.

The "spongy" grass is almost always a thatch buildup, not soil eroding from the original sod. The lawn was most likely over fertilized and watered which causes excessive growth. The other cause of spongy grass would be the wrong cultivar of st Augustine being used, I see it happen if you plant Palmetto St Augustine grass in full sun when it should be Floratam in full sun. Both of the recommendations of top dressing(with plain sand) will help for a while but if the cultural practices aren't corrected, then it will happen again within a couple years. I hope this is helpful.