GOOD IDEA!

WHAT WOULD I BE INSPECTING THE INSIDE OF THE HULLS FOR?? I HAVE A HOBIE 18 FROM 1985 WHICH IS IN GREAT SHAPE. THE OTHER DAY I WAS LOOKING INSIDE THE HULLS (DURING THE DAY) AND NOTICED THAT THE WHOLE BOTTOM SIDE OF THE HULLS WERE SOMEWHAT TRANSLUSCENT. THE LIGHT COMING THROUGH WAS NOT SPOTTY OR PATCHY, IT WAS EVEN FROM FRONT TO BACK AND CUT OFF ABOUT A COUPLE OF INCHES UP. THERE THE SIDES OF THE HULLS BECAME TOTALLY OPAQUE. I LOOKED AT THE HULLS FROM THE OUTSIDE AND ASIDE FROM SOME MINOR SCRATCHES THE HULLS WERE FINE. ANYONE KNOW IF THIS IS NORMAL OR WHY THIS IS??