Verified answer

because welding has absolutely nothing to do with fire as you know it.

Arc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. Because it uses electricity, you can arc weld anywhere. Underwater, in open air, even in outer space. That light you see is not fire, it's ultraviolent light (which is why it is dangerous to look directly at it.)

http://en.wikipedia.org/wiki/Arc_welding

http://en.wikipedia.org/wiki/Underwater_welding

BTW, what is this doing in the philosophy section?

Yes, hubby is right. Underwater welding is done all the time. Special torches provide the proper mix of gases and pressure to burn with intense heat. It's most commonly done in salvage work or jobs like repairing damaged oil rigs. Now, hug your husband and tell him you are sorry for EVER doubting his wisdom !

lighter fueled pyt it on the water and light it

Seen it done, never thought how.