Spotting an undercooked lobster involves observing several key signs, such as color. A fully cooked lobster is bright red with no trace of translucence or hints of blue and green.
Instead of opaque and white meat inside, an undercooked lobster has a translucent or jelly-like consistency. It may also emit a fishy odor rather than a sweet, ocean-fresh scent.
Finally, you can use a food thermometer. If it reads below the 145 degrees F mark when inserted into a lobster's thickest part without touching the shell, it's undercooked.