The PortMiami Tunnel (also State Road 887; formerly Port of Miami Tunnel) is a bored, undersea tunnel in Miami, Florida. It consists of two parallel tunnels (one in each direction) that travel beneath Biscayne Bay, connecting the MacArthur Causeway on Watson Island with PortMiami on Dodge Island. It was built in a public–private partnership between three government entities—the Florida Department of Transportation, Miami-Dade County, and the City of Miami—and the private entity MAT Concessionaire LLC, which was in charge of designing, building, and financing the project and holds a 31-year concession to operate the tunnel.