When taking a disabled sports craft in tow in coastal sea conditions, why must the length of the towline be adjusted so that both vessels are 'in step' (al paso) on the waves?

1. So that both vessels ride up on wave crests and descend into wave troughs simultaneously, preventing violent snatch loads and towline breakage
2. So that the towed vessel can use its radar to guide the towing boat
3. To ensure the towline drags along the seabed to act as a sea anchor
4. To allow the towed vessel's propeller to turn freely and charge its batteries