Skirt booms are a development of standard booms. They include a plastic-coated polypropylene fabric to enhance the standard boom, extending a few centimetres under the boom’s water line and acting as a skirt that sinks in the water. This additional element prevents oil passing under the boom which, once saturated, can continue to contain the spill efficiently; a clear advantage over the conventional absorbent booms.
Ref.: Absorbent skirt booms.