If you sail in central southern England, you’ll find spring high waters equate to midnight and mid-day. Down in the west country they fall around 0600 and 1800. On the Thames they’re usually in time for a latish lunch and so on. Neaps clearly come six hours adrift. We all know that tides follow the moon and that the top of springs will be a day or two after full moon or at new moon. Once you’ve sorted out when your local tides generally fall, you’ve only to look at the moon sailing through the clouds to predict what time tomorrow’s ebb will start running away, which is exactly how it was done before people could read tide tables.