You need a strong rope that will absorb the impact of the waves and sink, not float. Nylon meets all these requirements. Nylon anchor lines are lightweight, flexible, strong, and provide elasticity to relieve peak loads on anchors and boats. It is elastic and therefore has good shock absorption.Double braid is ideal for anchoring, combining decreased stretch with increased shock absorption.
How do I know what size of anchor rope do I need?
You should have 8 feet of rope for every 1 foot of water you will be anchoring in Your rope should have 1/8" of rope diameter for every 9' of boat. So this means a 45' boat would want at least a 5/8" diameter rope.