Possible Clues:

• In and out of season?
• It does twice daily turns at coastal resorts
• ''Time and . . . . wait for no man''
• An almanac lists its highs and lows
• Sounds as if such a diet will get one in and out
• It can ebb and flow
• Thing creeping up on a beach
• We hear it's bound to be a current variation
• It may be stemmed or turned
• Notable Bay of Fundy feature