Wet ice is frozen water while dry ice is solid carbon dioxide. Wet ice will melt at 0 degree celsius leaving a water residue. On the other hand, dry ice sublime at -78.5 leaving no water residue. In transporting specimens, wet ice is more ideal in short term transfers and not recommended in off site shipping because of the possibility that it may leak. Dry is preferred in cases of long shipment days due to its temperature and sublimation properties. In the United States dry ice is a class 9 dangerous good so it must be packaged accordingly. In conclusion, dry ice is much preferred in transporting specimens because of the minimal risk of contaminating the specimen.