I did a little snooping around about batteries and I believe bmtbandit has his batteries mixed up. Like you said heR3tic, Seadoo=Gel Cel. The biggest military application Lithium Ion or Lithium Ion Polymer battery I could find was a meager 14 Ah... and the price was, well, a couple would cost as much as the Seadoo.
I run AGM batteries in the tractors, my gas driven welder and my pickup (Optima's). My camper has an Optima blue top deep cycle AGM that you could use to weld with.... A couple of 12 volt batteries and a set of 25 foot welding cables makes an excellent DC stick welder for the field.
Optima batteries are made by Johnson Controls. If I were to go to a true spill proof battery, I'd get a Hawker Odessy. They will run in any position and have tremendous CCA ratings.
For an excellent charger go visit the other thread. My Vector is the last charger I'll ever buy. It charges everything, has a de-sulfation pulse current mode and runs a piddily 2 amps or less for little batteries or 100 amps for big batteries, all automatically and it shuts itself off when the battery reaches 14.5 volts and starts again when the battery voltage drops due to idle discharge.