UL is a portable lantern and a swimming buoy, which does not require any sort of batteries. It creates its own energy using salt water and magnesium blocks. It is meant to be used at seaside locations. UL is an ideal companion for long night chats with friends or swimming after sunset. As a result of double walls being filled with an air, it floats on the water. Moreover, partial submersion adds to its stability, resulting in UL gliding across the surface. In some seaside locations it is even required to use a reflective swimming buoy while outside of perimeter marked with buoys. UL enhances the function of reflective swimming buoys - it shines. That way anybody can swim in the sea at night and his friends can still watch over them from the beach. In order to use the lamp, it is needed to unscrew the lid with a handle (which is part of a technical core). After releasing the bayonet thread, take out the core and fill the container with salt water, then the lid can be put back on and fastened. The switch is placed conveniently in the cavity under the handle, in a perfect reach of fingers and, at the same time, safe from mismanagement. For using it as a buoy, it is necessary to lead a strap through a flat hole in the small lid, under the handle and back through the hole, then to fasten it with a buckle on the outside of the lamp. The small lid is there only for hydrodynamic purposes to prevent the handle cavity in the lamp from holding people back while swimming. As mentioned above, the body of the lamp has two walls, which means that the inner container can be filled with water and the lamp will still be able to float. All technical components are placed in the core - watertight LED straps, replaceable magnesium cathodes, carbon anodes (fixed) etc. The electric energy is created by a reaction between cathodes, anodes and the salt water, which acts as an electrolyte. Fresh water is required once every 8 hours of usage. One recyclable magnesium bar should be able to last minimum of 120 hours.