Rep. Harry Geisinger, R-Roswell, announced the 50-foot buffer legislation at a news conference held by the Georgia Water Coalition.
The marshes are state property, and some limits on development already exist under a law passed in the 1970s.
The new standard would affect private property surrounding the marshes.
"Today, we've got to go a step further because what we did in those days does not meet today's challenges," Mr. Geisinger said.
Mr. Geisinger's proposal lands in the middle of a months-long battle over how far the state should go in protecting the marshes. The Department of Natural Resources is bogged down in a debate over rules that would spell out how to police facilities such as parking lots and buildings connected to public docks, marinas and the like.
Those rules would also require a 50-foot buffer, but only around upland facilities such as the parking lots and buildings. Last month, the DNR board committee that oversees coastal issues ordered the department's staff to redraft the rules, which originally had just a 25-foot buffer.
Supporters say Mr. Geisinger's measure is needed to prevent storm water from sweeping pollutants into the marshes.
"This is a first step in meaningful protection of the marshes," said Gordon Rogers, the executive director of Satilla Riverkeeper. "We don't mean to say in any way that buffers are going to solve all our problems."
Opponents say the rules compromise private property rights by preventing owners from building on their own land.
But Mr. Rogers said one person's property rights do not allow him to spoil someone else's land - even if that land is owned by the state.
"Just because it's public property doesn't mean it gets less protection," he said.
It's unclear how far the legislation will go. Buffers around bodies of water have been controversial in the General Assembly for years.
A bill that would have weakened similar buffers for the state's streams passed the Senate last year before being voted down in the House.
Reach Brandon Larrabee at (678) 977-3709 or firstname.lastname@example.org.