How to Build Your Own Mushroom Anchor

Wipe the inside of a wok with a tablespoon of motor oil. Mix the concrete with the water until you have the consistency of a heavy cake batter and pour enough into the wok to create a three inch layer around the complete inside, up to the top edge.

Smooth the inside of the concrete using the bottom of a large spoon or other curved surface so that it takes on a "bowl within a wok" appearance in the wok. Put a slight incline with a trowel all along the top edge, so that the concrete nearest the wok is about 1/2 inch higher than the concrete edge on the interior of the bowl shape. Exactness is not necessary.

Wipe the PVC tubes with a thin film of motor oil. Punch the first one through the wet concrete until it contacts the metal wok. Do the same with the other four tubes at a distance of halfway up the wok and spaced equally distant around the bowl.

Allow the concrete to dry for 48 hours, then pull the PVC tubes from the concrete. Gently turn the wok upside down and let the concrete fall out into your hands. Set it in a dry, out-of-the-way place for 30 days.

Slip a nut and washer over the eyebolt and dribble a thin line of marine-use-approved thread locker around the bolt threads. Place the bolt through the center hole, from the inside of the bowl shape to the outside. Slip the other washer and bolt onto the eyebolt thread and tighten both nuts down until there is a firm connection. Brush a synthetic rubber coating over all the metal parts and let them dry.