The Fv863 runs 1.7 kilometres in tunnel under the Kvalsundet strait, from Kvaløya to Ringvassøya in Troms. When it opened in 1988, it was the first undersea road tunnel in the county.

The reason is that the rock ceiling sits only 25 metres below the sound, and at its deepest the road lies 56 metres below sea level. A shallow tunnel like this needs pumping equipment and a reserve basin for the leaking water, and it has both.

The tunnel binds the Tromsø region to Ringvassøya, and the sound has no other road crossing. When it closes all traffic must detour, so check the status before you drive.