TFA is just speculating a linear scale down to handheld and shark-mounted lasers as a joke. Pretty funny too.
The goal weapon is 150kW which will put out the .50s 17kJ in about .11 seconds.
Nothing mentions the diameter or frequency of the beam used, but as another person alluded exposed human parts would explosively vaporize, metal would melt, and clothing would ignite(sufficient to stop combatant) pretty quickly.
36.6C, 40kg body water raised to boiling 63.4 degrees.
40kg * 63.4C * 4.18kJ/(kg * C) / 150 kW = 70.7 seconds to boil a 40kg person.
But that isn't how it works, it's focused on say 20 cc of water. .02kg * 63.4C * 4.18kJ/(kg * C) / 150 kW = .035 seconds. So 20cc * 1700 = 34000cc BOOM!
So (according to wolfram alpha http://www.wolframalpha.com/input/?i=.035+s) between .4 to .7 of a "blink of an eye" 20cc of water turns to 34000cc of steam with what was a part of your body...and nobody said they turn the beam of here.
That probably over-simplifies how the energy would be converted and propagate through tissue, but who knows the frequency or diameter of the beam?