If you're hiking or exploring the bush and you lose or bust your compass you can make a rudimentary compass by floating a magnetised needle. Instead of looking for a pond or puddle to hold your needle you can pour water into a ziplock bag to provide a stable surface for your needle to point north.
Wilderness survival expert Dave Canterbury recommends carrying a magnetised sail needle, a fishing float and a freezer bag for this purpose. Canterbury is opposed to unitasker items in the wilderness so each item he carries must perform multiple functions — the sail needle is large enough for repairing gear, sewing leather, or using to remove splinters; the float is also used for improvised fishing; and the freezer bag can hold water or wild edibles and also be used to mix flour and water into dough while camping without a mess. Which is why I recommend this method over the method we covered last year that requires a bowl made of duct tape.
You'll need to have already magnetised the needle for this to work. You can buy a magnetiser/demagnetiser tool at a local hardware store for a couple of bucks. As Mr Canterbury mentions in the video above, leaving a needle in the magnetiser for a few days will keep it magnetically charged for months. The tool is small enough that you can also carry it with you if you like.
As the video above demonstrates, simply fill a freezer bag full of water, insert the needle into the fishing float so it will float and close the bag and wait for the needle to stop moving; it will point to magnetic north (as opposed to true north).
Improvised Zip Lock Compass [YouTube]