A more thorough explanation:

CUSTOS MARIS

Custos maris is a Latin term that means "warden of the sea." In history, it referred to a high-ranking naval officer, also known as an admiral. It was also called seaward or seward.

During the 16th century, the custos maris was responsible for protecting the seas from pirates and enemy ships.

Queen Elizabeth I appointed Sir Francis Drake as custos maris to lead the English fleet against the Spanish Armada in 1588.

The examples illustrate how custos maris was used to refer to a high-ranking naval officer who was responsible for protecting the seas and leading naval operations. Sir Francis Drake was appointed as custos maris to lead the English fleet against the Spanish Armada, which shows how important this position was in naval warfare.