They would use it to know when the tides are in and out, which could be important for them when they are planning a journey. If they are going into a port with a large boat and the tide was too low, they could run aground. If they are trying to launch a boat from land, they would want a high tide to make it easier. There are lots of other reasons why they would want to know what the tides are at, so the tidal tables would be important for them.
Water Depth
weather depth
Water depth
water depeth
water depeth
Water depth
Water depth
Water depth
Water depth
Water depth
Tide tables tell boaters whether there will be enough water to navigate in. They tell you when high tide is or Low tide. If your boat requires three feet of water to operate and at low tide there is only two feet the boater has to wait until the tide comes in.
To check on the incoming and out going tides in their area so that when leaving port they are the high tide and arriving again at high tide it stops the ship grounding.