Underwater Kinetics Blue Tang Hydralloy SS Knife, Blunt Tip - Yellow. The Underwater Kinetics Blue Tang Hydralloy SS Blunt Tip Dive Knife is UK's improved-take on the classic, multi-functional dive knife. UK has patented their own Hydralloy steel for a blade that is both strong-and-corrosion resistant where most competitors' blades only offer one of those features. The special Hydralloy utilises a unique-blend of metal-alloys and proprietary-finishing techniques to provide a knife with the strength of 420-stainless steel, while exceeding-the-corrosion resistance of 316-stainless steel.