One thing I have found to do with some of the pot buoys salvaged from the beach (and it doesn’t matter if they have a puncture or a split) is turn them into unusual garden lanterns.
Splice (it’s fun to learn and here’s a stepwise instruction, but tie it on otherwise) a bit of beach found rope to the eye of the buoy. Remove the valve stopper with a screwdriver and drill out (6mm should do) the valve just wide enough to slide an old piece of electrical appliance flex into the buoy; vacuum cleaner flexes are good as they are nice and long and usually have a moulded on plug too.
Turn the buoy eye down and mark 3/4 of the way around a circular object placed on the buoy; a 1 litre paint tin works for me. Now cut a 3/4 semicircle (I know but you get the idea) in the other end of the buoy to create a flap just enough to get your hand in. The plastic is quite easy to cut with a fresh ‘Stanley’ knife blade but look out for your fingers.
Pull the wire through, strip 2 inches (50mm) of the sheath from the flex and 1/4 inch (5mm) off the ends of both the blue and brown wires (cut away the green and yellow earth wire to the sheath of the flex). Wire on a pendant light fitting (unscrew the 2 parts of the pendant, thread the wires through the ‘cup’ part, fix one to each terminal of the bulb holder part (it doesn’t matter which way round) and hook the wires under the lugs on the bulb holder before screwing the two parts back together). In an ideal world there will be no wire showing from the pendant only the sheath of the flex, but it’s often a matter of practice to get the wires exactly the right length. Attach a cable tie to the flex 2 inches (50mm) or so above the light fitting to stop the flex pulling out of the buoy or the wires getting strained and fit a low energy bulb.
Draw the flex back and cable tie the electrical flex to the rope. Change the fuse in the plug to 3amp.
Now hang the buoy up and use silicone sealant to seal around the flex where it enters the valve of the buoy making sure you get the sealant right down around the flex. Leave it unmoved and allow 24 hours for it to cure and ta da!
Obviously if you are unsure about wiring the lamp holder yourself get some help it really requires only a low level of competence, though a qualified electrician will probably not want to put their name to the project. And even more obviously and this is only common sense, if you are going to use these outside put a circuit breaker between socket and plug and don’t let (rain) water get to the electrical connections. I have had these outside all through winter in all weather and they have been just fine so I know if the job is done thoroughly it will be just fine.