LINCOLNVILLE, Maine — Coastal Route 1 in Lincolnville, just south of the Northport town line, was busy on a recent rainy morning as cars and trucks zoomed loudly by. But just a short walk away from the road was something of an oasis: a 4-acre parcel of oceanfront property that has been offered as a swap to the town by the Coastal Mountains Land Trust in exchange for 68 wooded inland acres on the Ducktrap River. “It’s beautiful,” David Kinney, the Lincolnville town administrator, said of the park, which has 426 feet of shore frontage.