Magnesium burning underwater

Today in science we tried an experiment. This experiment was watching mg (magnesium) burn under water. Unfortunately the mg only burned for a split second when put under water.

Here is an experiment of magnesium burning in air. As you can see, it creates a very bright light when burning.

Why is it that magnesium creates such a bright light: The main reason that it burns so brightly is that when it ignites, it becomes extremely hot. Mg meets O2 and creates MgO which gives off heat and heats with the mg metal. This reaction's speed varies according to the temp of the gas fire. The hotter the gas fire, the quicker the reaction and the quicker the mg burns.

If the variables all work with you, the burning Mg can even burn in water. See below ( this is not my experiment it belongs to scitube )

How come the burning magnesium stays burning in the water? 'To my knowledge, neither of these metals "burn" underwater. The word burn generally suggests that something reacts with oxygen. As others have stated above, these very active metals will react with water by displacing hydrogen as H₂. The hydrogen definitely will react with oxygen assuming that enough heat is evolved to start the reaction (very likely for sodium, less so for magnesium).' ChemProfMatt

To me this means that it still reacts with the oxygen in the water and turns the hydrogen into H2. The reacting of the oxygen and mg ( MgO) keeps the mixture hot enough for the magnesium to stay burning.