Yes, flares can light and burn underwater. They contain their own oxidizer, allowing them to burn without atmospheric oxygen. While the flame might appear less intense due to water pressure and cooling, the chemical reaction still occurs, producing light and heat.
No, standard flares are not designed to work underwater for signaling purposes. They require oxygen to burn, which is absent or severely limited in an aquatic environment. Attempting to use a conventional flare underwater would likely result in it failing to ignite or quickly extinguishing. Specialized underwater signaling devices exist, but they are distinct from typical surface flares used for distress or illumination above water. They serve different functions.
Flares primarily rely on an exothermic chemical reaction that requires an oxidizer, typically oxygen from the air, to sustain combustion. When submerged underwater, the immediate lack of available oxygen prevents this reaction from occurring or continuing. The water also acts as a powerful cooling agent, rapidly drawing heat away from any potential ignition point, further inhibiting the flare's ability to burn effectively or even ignite in the first place. It's a fundamental design limitation.
While traditional flares do not work underwater, there are specialized pyrotechnic devices designed for underwater use. These are not typically called "flares" in the conventional sense but serve similar signaling or illumination purposes. They often use different chemical compositions that can generate their own oxygen or burn without external oxygen, allowing them to function in an aquatic environment. These are usually for military, commercial diving, or scientific applications, not general recreational use.
If you attempt to light a standard flare underwater, it will likely fail to ignite. Even if a small spark is generated, the surrounding water will immediately cool it, preventing the sustained combustion needed for the flare to function. The lack of oxygen will also starve the chemical reaction. In most cases, the flare will simply get wet and become useless, without producing any significant light or smoke. It's not designed for that environment.
No, a standard marine flare, despite being designed for use near water, is not intended for underwater operation. Marine flares are for signaling on the surface of the water or in the air, where oxygen is readily available. Submerging a marine flare would prevent it from igniting or cause it to quickly extinguish due to the lack of oxygen and the cooling effect of the water. They are for surface distress signals.
Standard flares cannot be modified to burn underwater effectively. Their chemical composition and design are specifically for atmospheric combustion. To create a device that burns underwater, you would need a completely different pyrotechnic formulation that either generates its own oxidizer or can sustain combustion in an anoxic environment. This is a complex engineering challenge, not a simple modification of an existing flare. It's a different technology.
No, distress flares, whether handheld or parachute types, are designed exclusively for use above water to signal for help. They rely on atmospheric oxygen to burn brightly and produce smoke or light. If submerged, a distress flare would not ignite or would quickly extinguish, rendering it useless for its intended purpose. For underwater distress, specialized acoustic or electronic signaling devices are used instead. They are not interchangeable.
Many light sources work effectively underwater, but they are not flares. These include waterproof flashlights, dive lights, chemical light sticks (cyalume), and specialized underwater strobes or beacons. These devices are designed to be sealed against water intrusion and often use batteries or chemical reactions that don't require external oxygen. They provide illumination or signaling capabilities in an aquatic environment, unlike traditional flares which are air-dependent. They are purpose-built.
Attempting to use a standard flare underwater poses several safety concerns, primarily that it won't work, leaving you without a signaling device if needed. If by some unlikely chance a flare partially ignites, it could produce toxic fumes or a brief, uncontrolled reaction in an enclosed underwater space. The primary concern, however, is the false sense of security or the wasted effort in relying on a device not designed for the environment. It's generally ineffective and potentially hazardous.