A 4-acre piece of waterfront land in Boca Raton is hitting the market for $43M, a development opportunity buyers will have to "sea" to believe.

Delray Beach resident, investor and local developer William Swaim has put a 4-acre plot up for sale that is largely submerged under Boca Raton’s Intracoastal Waterway, The Palm Beach Post reports. He told the paper that he is willing to fill in the land and build a seawall for a buyer for an additional $3.5M.

Swaim has been in a legal tussle for the title and right to sell the parcel, located in an area north of Lake Wyman and submerged south of Spanish River Boulevard. In 2018, Army Corps of Engineers personnel deemed that the land could be developed without disrupting the habitat of local endangered and threatened sea turtles, smalltooth sawfish or manatees.

Local environmental group Everglades Law Center disputed the notion that development wouldn't affect wildlife in the area.

“I think we are getting to the point where we can’t afford to lose any more seagrass in our waterways,” Everglades Law Center Executive Director Lisa Interlandi told the PBP. “Manatees are dying at record rates because of impacts to their habitat, and increasing development on submerged lands is only going to compound that problem.”

In 2016, Swaim sued the state, the Palm Beach County property appraiser and five fiber-optic companies over ownership of the land, the PBP reported. Those firms ran their cables through the land and mud into the Atlantic Ocean adjacent to Swaim's property.

The parcel had been above sea level until 1957, Swaim told the PBP, until its dirt was taken by a neighboring resident who was granted a permit by the city to develop a subdivision in the vicinity. If the land is refilled, it is zoned for single-family residential development.

It is unclear how much submerged land is privately owned in Palm Beach County, but there are a handful of examples of development battles that have played out in recent years. The $600M Bristol condominium building in West Palm Beach was built on formerly submerged land.