46 CFR §140.605

1. (a)Prior to getting underway, and at all other times necessary to ensure the safety of the vessel, the master or officer in charge of a navigational watch must determine whether the vessel complies with all stability requirements in the vessel's trim and stability book, stability letter, COI, and Load Line Certificate, as applicable.
2. (b)A towing vessel must be maintained and operated so the watertight integrity and stability of the vessel are not compromised.