Complex sentence: To maintain the catenary shape in the presence of wind, a heavy chain is needed, so that only larger ships in deeper water can rely on this effect--smaller boats must rely on the performance of the anchor itself.
Split into simpler sentences: To maintain the catenary shape in the presence of wind, a heavy chain is needed, so that only larger ships in deeper water can rely on this effect. Smaller boats must rely on the performance of the anchor itself.