Cocoa Beach is the best and closest beach to Orlando Florida. That is most of Orlando Florida. Daytona Beach to the north of Downtown Orlando is great and Clearwater Beach on Florida's gulf coast is the best in the entire state and has the best surrounding area for visitation. All three are slightly different and a preference will have to decide.
Cocoa Beach is on the Atlantic Ocean (technically all of these are) located about an hour east of Orlando Florida if you take the fastest routes. This is a relatively small town on a barrier island on Florida's east coast about five miles from north to south. The soft sand is a nearly pure white sand that makes beautiful beaches what they are. While not necessarily a famous beach if your on an Orlando vacation craving a beach day this one is just about an hour's drive and well worth it.
To the north is Kennedy Space Center and Cape Canaveral National Seashore. Also in that area is a huge marina that is worth seeing. Most overlook these places and even Indian River and Indian River Lagoon because they are focused on getting to that beautiful beach.
Daytona Beach is just an hours drive from downtown Orlando FL. This is another beach located on Florida's east coast and it is famous for many things. This is a popular destination because of the Daytona Beach Speedway, Daytona Beach Bike Week and it is a popular spring break destination. It doesn't hurt that it is just off the interstate which is rare for a Central Florida beach.
Daytona beach can also be a relatively family friendly beach. It is more than just a party town. There is deep sea fishing, the quintessential beach town etcetera but basically this is a typical Atlantic Coast beach that just happens to be relatively near Walt Disney World and the Orlando area.
Actually my favorite beach has to be on Florida's gulf coast for many reasons. It is just an hour's drive to downtown Tampa and 25 minutes more to Clearwater Beach. Realistically a two hour drive with likely traffic is the norm. The sand dunes, beach breaks and sugar white sand are just a few of the reasons this is among the most popular beaches in the nation.
A dream destination for many and certainly within walking distance of most hotels. This area is mostly suited for multi day trips. Boogie boarding, paddle boarding and every other activity can be done on gulf beaches and the pier here is second to none. St Pete Beach is 20 minutes south.
Volcano Bay in Universal Studios, and two other water parks in Disney have beaches with blue waters and even sand. No jet skiing, body surfing, boogie boards or even a paddle board but lazy rivers make up for their absence and so do the adjacent theme parks.
Ok, so close to two hours away and honorable mention goes to Ormond Beach, Ponte Vedra Beach, New Smyrna Beach, St Augustine, Flagler Beach and one of my favorites Vero Beach. I think you are beginning to see why so many people fall in love with Orlando Florida.