The management of ships’ ballast water has emerged as a significant environmental and operational challenge for the global shipping industry over the past few decades. Ballast water, essential for the safe operation of vessels like bulk carriers to control stability, trim, and stresses, can inadvertently transport thousands of aquatic organisms and pathogens from one ecological region to another. The introduction of these Harmful Aquatic Organisms and Pathogens (HAOP) into new environments can have devastating ecological, economic, and public health impacts, disrupting local ecosystems, damaging fisheries, and introducing diseases. In response to this global threat, the International Maritime Organisation (IMO) adopted the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWMC or BWM Convention) in 2004, which entered into force on 8 September 2017. This convention establishes global regulations to control and manage ballast water and sediments, requiring ships to implement specific procedures and often to install sophisticated treatment systems. For the Master and crew of a bulk carrier, understanding and complying with the BWM Convention and operating any installed Ballast Water Management System (BWMS) correctly are now integral parts of their duties. This chapter will delve into the requirements of the BWM Convention, the methods of ballast water management (exchange and treatment), the operational aspects of BWMS, record-keeping, and the Master’s responsibilities in this critical area of environmental stewardship. This knowledge is vital for modern maritime operations.