Hammerhead Hull's unique chemistry vacuum allows for multitasking, saves time and effort.Apply when needed and leave on; remove at your convenience. Hammerhead Hull Cleaner is safe on most surfaces, including aluminum hulls. Will not damage aluminum or pit trailers. Hammerhead Hull Cleaner is formulated to target tannic stains caused by plant decay. Hammerhead Hull's vacuum emulsifying agents create dual cleaning action of both marine biofouling along with dirt and grime.