Heat Jaws had Ripjaws' torso, head and tail flap, but had Heatblast's arms and legs. Also, Ripjaws's dorsal fin is replaced by flames.
Heat Jaws suffered extreme problems. His Ripjaws half needs to stay out of the heat or he'll dry out, but Heatblast's half constantly generates heat, making him dry out quickly. His need for water caused his Heatblast half to get hurt. He couldn't stay in the water, even though it is crucial to Ripjaws, because it would extinguish Heatblast. Ben said that Heat Jaws was "not the best combo", as a fire alien and a water alien don't really mix as it cannot survive either on land or in water.