A dive flag is a low cost piece of kit but one day it could save your life. Although you can buy them, it is easy to make your own. Here's how.

First, the shopping list:

1 metre of 2oz red nylon fabric
2m 20mm plastic conduit
4 20mm straight couplings
2 plastic balls with 6mm holes drilled through
3m 5mm shock cord
White reflective tape
Plastic glue

The fabric came from a camping/outdoor shop (Carter's of Reading), the rest from B&Q - should come to less than £10. A metre of fabric is more than you need, but you'll have some spare just in case you need to make another.

First, cut the plastic tube into 4 equal lengths 50cm long. Drill a 6mm diameter hole about an inch from the end of one of the pieces. Loop about 25cm of the shock cord through this hole - this will serve as a wrist strap and also keep the flag together when not in use. Next, glue a straight coupling onto each of the pieces. Allow to dry, then thread the shock cord through the pieces of tube. Put a plastic ball at either end. Tie a knot in one end, then pull the other end taut (about 30cms of stretch is plenty) and knot it. You should end up with something like the picture.

Cut the fabric to size so it fits the tube at the top end between the couplings. It should be about 48cm high and 54cm wide (this allows for it to wrap around the tube), with about 1cm doubled back on each side and stitched. If like me you have no idea how to sew you'll have to find someone to do it for you on a machine!

Finally, put a diagonal stripe of the white tape on each side of the flag and sew this on for strength. Your flag is now ready for use! I keep mine attached to the left hand side of my twinset with some 5mm bungee loops, just behind the wing. Be warned, they can get tangled in shot lines - I have lost one already...