have many small tanks for the storage of ballast water. This prevents water
moving about, and upsetting the balance of the ship. Oil tankers have ballast
tanks in the space between the inner and outer hull and bulk carriers have side
ballast tanks. As these ships are loaded, ballast water is pumped out to keep
the ship within the load lines. When tankers and bulk carriers unload or
discharge their cargo, ballast water is pumped in. Marine pests, which
live in the sea, can be carried in shipís ballast water from one part of the
world to another. If this ballast water is discharged in a foreign marine
environment, it can cause major harm.
This makes the ship heavier and keeps it to the correct draft.