Patrol of officers who police a harbor area WordNet 3.0 & Open English WordNet

Water police, also called harbor patrols, port police, marine/maritime police, nautical patrols, bay constables, river police, or maritime law enforcement or coastal police are police officers, usually a department of a larger police organization, who patrol in water craft. Wikipedia

Group of police officers who enforce the law on water Wikidata

The police department charged with patrolling harbours and waterways by boat. Wiktionary

Police department charged with patrolling harbours and waterways. Wiktionary (translation)