[Castout]

Though the floating wire is now quite long(2000 feet to 2400 feet) your speed must be low in order to have a radio link with the wire.

This is because the wire's tension needs to be low in order it to float successfully to the surface.

If you are traveling at high speed or more than 5 knots the wire would be dragged under by the seawater above it because the wire starts from the sub itself all the way to the surface and hence a portion of it will always be underwater and hence that portion will be dragged under by your excess speed which is causing the seawater flow around the submerged wire to drag the whole wire down(increasing the wire's tension).

Increasing the buoyancy of the floating wire will not help you gain more speed but rather merely increases the depths at which you could establish radio link with your wire. Your speed will still be limited to about 5 knots. This is due to the reason I explain above.

So now the advantage of having such a long floating wire is merely to increase the depths at which you still could establish communication with the fleet.
Now it is possible to establish radio link at depth of more than 300 feet(100m) only if you are traveling at slow speed(about 5 knots).