Heres a rough take on the Water Knife concept

Water Knife-10: RKA 1d6, 8 Continuing Charges lasting 1 Turn each (+0), Armor Piercing (+1/2), Penetrating (+1/2), Continuous (+1) (45 Active Points); OAF Bulky Fragile (-1 3/4), Gestures (-1/4), Limited Range (-1/4), Reduced By Range (-1/4), Beam (-1/4), Concentration (1/2 DCV; -1/4)

Notes: System consists of a backpack type tank unit with an armored hose running to a spray nozzle mounted on the back of the wrist. designed for use in boarding actions, cutting holes in things... I could see definite rescue applications especially in areas where you could be dealing with gas leaks/flammables. its not really a weapon other than for an improvised melee weapon... it will cut through a spacesuit or most light body armor like butter though.

I gave it the concentration limitation due to the firer having to hold the water jet on target