Final answer:
The bell's admonition warned sailors about a nearby reef.
Step-by-step explanation:
The bell's admonition warned sailors about a nearby reef. When the bell on board a ship rings, it is typically used as a warning signal to alert the crew members about a potential danger. In this case, the bell was used to warn the sailors about the presence of a nearby reef, which could cause damage to the ship if they were to sail too close to it.