Because tides can change the depth of the water by an important amount. Underwater obstacles you can pass at high tide might catch you at low tide. Or even leave you stranded.
Tides can also cause strong currents. Usually not a problem for motor boats, but they can bring sail boats/and really slow motorboats to a standstill.
hurricans
hurricans
It can be a sign of bad weather
hurricans
hurricans
It can be a sign of bad weather
It can be a sign of bad weather
hurricans
hurricans
It can be a sign of bad weather
hurricans
It can be a sign of bad weather
hurricans
hurricans
It can be a sign of bad weather
hurricans
It can be a sign of bad weather