Often in the movies, people will declare that there is this urgent deadline for characters to get to a ship, because ‘it sails with the tide’. What’s that all about? Does a boat sail at high tide? Low tide? With the changing tide? And since they change several times a day, why wouldn’t someone hold the ship another twelve hours or so?
There are a few reasons why a ship will opt to sail at a certain time relating to tide. Probably the most common reason would be water availability in the harbor. Some harbors are simply too shallow at low tide for large ships to maneuver. Another common reason would be current. Some rivers and or harbors will have very strong currents while the tide is changing and this often causes problems for the less maneuverable vessels. The time period between high and low tides, when there is little to no tidal current, is called slack water. Often, ships will opt to sail during slack water so they don’t have to deal with currents.
A third reason is maneuverability while transiting a waterway. Ships and boats are more maneuverable when they are traveling against the tide. While their speed is decreased, their handling increases. Conversely, a ship or boat traveling with the tide is a bit harder to control and turning becomes more challenging due to the water flow pushing the boat from behind.
I am not a sailor. but the tide is a surge of water either going in your direction or the opposite. In the days before tug boats I imagine getting in and out of the harbor is a bit tricky. As far as holding the ship goes, I think it’s a lot like today; ya gotta be a VIP to change the schedule.
Scruloose hit the key. Often you would need the high tide to make it over sand bars in the harbor in your laden ship. Conversely, in a wide, shallow harbor, the outgoing tide could help your sailing ship exit the harbor in times of slack wind. But primarily the first reason.
I’ve also seen large ships have a maximum tide level that they can safely transit under a particular bridge.
Not only before tugboats, but also before motors - you needed the tide-generated current to help carry you out of the harbor. It was also desirable to have deeper water to aid in not running aground, but the main use of the tide was the assist in getting out to sea.
Obviously, this means that the desirable time to weigh anchor was shortly past the time of high tide, on the ebb.
On my sailing trip, I asked how they used to get in to a harbor if the wind was against them. One of the crew told me that they’d attach a line to the capstan on the ship, and take the other end out in a rowboat and tie it to a piling near the mouth of the harbor. Then they’d wind the capstan (by hand, and feet, and back) to haul themselves in.
If I could get a little help from the tidal current, I’d take it.
Known as warping.
Just a fairly minor nit-pick or clarification; slack water is the time around high or low tides…
Thanks for all the info, guys!