Lindgren-Pitman's best 400# Red mono.  Large offshore knots crimped with long aluminum oval swivels on each end.

The Offshore Loops are perfect for large d-ring connections to the planer board and boat.

Available in 75, 100, 125 and 150 foot lengths.
There are two tow lines in each package.

Chesapeake Bay planer boards

NOTE: The picture shows a Long Line release clip that was a custom rig.  As described above, there are offshore loop knots at each end.