It's "Mad Beach" to the locals, and occupies the last two miles of the southern end of Sand Key in Pinellas County, Florida. At the southernmost end is John's Pass, famous for its grouper fishing fleet and John's Pass boardwalk, filled with shops and restaurants.
Madeira Beach provides two main public beach accesses and plenty of street-end accesses, many of which have limited, metered parking. It attracts "recreational beachgoers," not "peace and quiet nature-lovers."
The Tom Stuart Causeway (S.R. 666) will take you right to the northern reaches of Madeira Beach, just south of Redington Beach. Madeira has lots of small beachfront resorts and rental condominiums. There are also plenty of funky older beach houses within a block or two of the beach.
The water here is great for swimming and wading and the beach sand is generally white and soft. You will have to pay to park at any of the beach access points, but if you are staying on the beach or within a few blocks of the beach, that won't be an issue.
If you stay nearer to John's Pass, you can walk to just about anything you might need or want. In fact, you can walk from the beach to the shops at John's Pass by using the walkway underneath the new John's Pass Bridge. You don't even have to cross the busy road.
The City of Madeira Beach website has lots of info on this busy Gulf Coast island town.