Lake Harney straddles the Volusia-Seminole county line along the St. Johns River. The lake is part of the St. Johns Wet Prairie of the Eastern Flatwoods District (Brooks and Merrit, 1981). The series of lakes along the St. Johns River in this area occupy valleys previously incised by Late Pleistocene fluvial-lagoonal processes. The area is low-lying and predominantly marshland. Lake elevation at the time of the seismic survey was ~1.8 m (6 ft) NGVD. Gopher Swamp appends to the east, separated from the lake by Stone Island. Black Cypress Swamp is connected to the lake via Underhill Slough to the northeast. The St. Johns River enters Lake Harney from the south and flows out to the north. Lake Harney is roughly oval in shape, with 20 km (12 mi) of shoreline and a surface area of about 24 km².