An "undeveloped beach" refers to a beach that has not been altered or modified by construction or human activities. It remains in its natural state, preserving its original features like sand, vegetation, and wildlife. Full definition
This area has miles of undeveloped beach adjacent to the headlands. (en.wikipedia.org)
It's not all bad though, as both islands have their share of beautiful undeveloped beaches, beachbums are well catered for. (travelfish.org)
New Chums Beach is one of the last undeveloped beaches in the Coromandel and has been voted one the top deserted beaches in the world! (stokedforsaturday.com)