If you're out on the water regularly on any type of craft, a sea anchor is an important piece of equipment to have with you. The sea anchor has many uses, but primarily it exists to help stabilise a craft in choppy weather. Sea anchors don't sit on the ocean floor, but instead are meant to anchor the boat to a spot in the water, or to slow down its movements considerably. Sea anchors are also known as drogues.
Cut a rope of the proper length for deploying a sea anchor. There are various guidelines that exist for how much rope you want, and an experienced user of your particular model may give you advice on shorter or longer ropes based on how your craft handles in rough water. Barring that, choose a rope that is equals 10 feet of length for every foot in length of your boat.
Make the anchor itself out of a piece of canvas cloth, or buy a premade parachute anchor. The sea anchor itself is a piece of heavy canvas or cloth that acts like a parachute dragged behind the boat to slow its movement. If you want to make your own very simple sea anchor, you can cut a triangle out of canvas. Make it an equilateral triangle that measures 3m per side. Otherwise, you can purchase a more sophisticated parachute anchor.
Weight the bottom of the sea anchor if you are not using a premade anchor. A premade anchor parachute might have weights already in it to make sure that one side of the anchor stays down. You can fold over the cloth and sew a tube into it and run a steel rod through it to weight your own. Then attach sinkers to each end of the rod. This should keep your anchor in the correct orientation. Bend the rod at the end to keep it from falling out of the loop and to create anchor points for ropes.
Attach a bridle to the anchor itself. You can purchase a bridle that is already made to attach to your anchor. Otherwise you can attach ropes to work like bridles to the loops on your rod. Fold over the fabric again and create loops on the other two sides to thread rope through and create a loop at the top of the anchor. On the bottom two corners, attach bridle ropes to the loops in your metal rod and then attach the third bridle rope to the loop at the top of the anchor. Attach all the bridle ropes to a swivel. If you are using prebought elements to build a sea anchor, you will find that your parachute and bridle have many more than three attachment points. The swivel connects to your primary anchor rope.
Tie a retrieval line on to the top of the anchor. Attach it to the same top loop that you used to attach the bridle to or to the proper spot for the retrieval line that you will find on a purchased anchor. Attach a float to the top of the line so that you can retrieve the sea anchor.
Run a line from the float and the float rope back to your boat so you can collapse and pull the sail in when you are finished using the anchor.
You can use as many homemade or prepurchased elements as you want, or use a combination of them to build a sea anchor. When making your own components, make sure that all connection points on the device are strong before you use the anchor. Your safety can depend on it.