The Giants were rocked by back-to-back defeats at the hands of Super League title rivals St Helens and Catalans Dragons but have been back to their gritty best over the past week.
Watson's team left it late to beat Warrington Wolves last Saturday and the clash with Hull FC followed a similar pattern.
The Giants did not lead until the final 10 minutes against the Wolves and left it even later on Friday night to break Hull hearts.
Danny Levi was the Huddersfield hero, scoring his first try with six minutes remaining before making sure of the win with the Black and Whites out on their feet.
While it was not pretty, it was another example of why the dogged Giants will be a genuine force in the play-offs.
Whereas Huddersfield look assured of a top-four spot, Hull's play-off chances remain in the balance.
But Brett Hodgson would have been encouraged by what he saw from his team as they built on their win over Toulouse Olympique with another positive display, particularly with four home games still to come.
The first half was bookended by Hull tries to leave the visitors in control at the interval.
It took only four minutes for the Black and Whites to open the scoring thanks to Jack Walker's first try for the club.
The Giants failed to deal with Jake Connor's reverse kick close to their own line and were helpless to prevent the centre from putting Walker over.
Luke Gale missed the touchline conversion but Hull had laid down an early marker.
Clearly buoyed by the win in the south of France, the Black and Whites had a steely look that was absent during a recent four-game losing run that saw Hodgson's side concede 196 points.
As well as Hull defended in the first half, Huddersfield were clunky with ball in hand to continue a recent theme.
The Giants forced several drop-outs but rarely threatened to breach a resolute defensive line.
Even the presence of Tui Lolohea in his first outing in four weeks could not get Huddersfield firing, the full-back showing signs of rust with a loose pass as the hosts tried to turn the screw.
At the other end, Connor almost laid on a second try after creating space for Josh Simm only to see the winger fail to take in his pass.
The Giants pride themselves on winning the territory battle but Hull were strong through the middle in the opening half an hour.
After substitutes Levi and Jack Ashworth injected some life into Huddersfield, Luke Yates was held up during a period of sustained pressure.
But Hull hit the hosts with a sucker punch through Connor Wynne four minutes from half-time.
Walker was the architect, taking Jordan Lane's inside ball and getting a nice offload away to allow Danny Houghton to put Wynne over.
Gale was on target from the tee to make it 10-0 but only after Will Smith was belatedly sin-binned in the aftermath of the try for apparent foul play.
Huddersfield eventually punished the Hull new boy four minutes into the second period after going close through Leroy Cudjoe just before the break.
Fancy footwork from Will Pryce left Hull on the back foot and Lolohea took advantage after pouching Cudjoe's offload close to the line.
Smith returned to the field after seeing Pryce cut Hull's lead to 10-6 from out wide and he helped his side deliver an instant response.
Giants old boy Connor was the creator, sending through a grubber kick that was smartly finished by loanee Ellis Longstaff.
Gale made no mistake from the tee to give Hull a commanding lead with half an hour to go.
Huddersfield upped the intensity but points were not easy to come by, Chris McQueen held up by more committed defence.
The turning point came just after the hour mark when Walker threw a forward pass in the act of preventing a 40/20 from Lolohea.
The Hull full-back was duly punished with Fages going over out wide on the right from the scrum.
Pryce added the extras to get Huddersfield back to within four points and the Black and Whites were unable to turn the tide.
Simm forced Ashton Golding into touch with a strong tackle but that only delayed the inevitable with Hull eventually buckling under intense pressure.
Levi went over to spark joyous scenes and repeated the trick in the final minute to give the Giants the kind of hard-fought win that steels them for the play-offs.
Huddersfield Giants: Lolohea, Golding, Cudjoe, King, I Senior, Pryce, Fages, Wilson, O'Brien, Trout, Jones, McQueen, Yates.
Substitutes: Levi, Greenwood, Ashworth, Hewitt.
Hull FC: Walker, McIntosh, Connor, Wynne, Simm, Smith, Gale, Evans, Houghton, Taylor, Lane, Longstaff, Fash.
Substitutes: Satae, Laidlaw, Brown, Lovodua.
Referee: Marcus Griffiths.