Smit crashed over in the corner for his side's fourth and final try to not only clinch a bonus point, but also make the game safe in the face of a spirited Blues revival.
That try capped an eventful second half for Smit, who came on after the break as a replacement tight-head prop. No sooner had he scored the try than he left the field with blood gushing from his head.
The Sharks made it four out of four in the Super 14 as they piled on the agony onto the Blues, who were hammered in South Africa by the Bulls on their travels earlier in the tournament.
The pace of the Sharks caught the Blues on the hop and hot on the heels of his two tries last weekend Springbok wing JP Pietersen added another to his collection, this time from deep in his own territory in the first-half.
Flanker Jacques Botes and lock Steven Sykes scored the other tries for the visitors, who now move on to face the Queensland Reds next weekend.
South Africa's other unbeaten side, the Bulls, beat the Stormers 14-10 in a brutal and highly tactical match.