@gontram
Phosphorous actually are stored underwater... they just can't burn in any sustaining rates, because the P2O5 formed by phosporus burning will be hydrolized with water to form H3PO4 which is good thermal absorber... Saltpeter are nitrates of alkali metals, and M-NO3 are ionic ones, they will be ionized in waters, so they can't burn... Sulphur is probably right, but I think it must be used in conjunction with some organic molecules (eq alkanes, aromatics, or heavy-fraction alcohols).... anyone has the exact composition?

@Marcus
That guy, made your head explode? oh Come on, they can only fire twice, and after that, they are easy pickings... but their two shots can take all Marshall of the Templars.... it was a sad story to not see the best-graphical projectiles in Kingdom, didn't make it in EB II...