tidesman

from The Century Dictionary.

• noun One who is employed only during certain states of the tide.
• noun A tidewaiter.

from the GNU version of the Collaborative International Dictionary of English.

• noun A customhouse officer who goes on board of a merchant ship to secure payment of the duties; a tidewaiter.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A customhouse officer who goes on board a merchant ship to secure payment of the duties; a tidewaiter.