What is the tidal datum in reference to in regions with ...

[abarnes]

What is the tidal datum in reference to in regions with semidiurnal mixed tides?
  a. Mean lower low water
  b. Mean low water
  c. Tidal range
  d. Mean tide

Question 2

What is needed to calculate the speed and direction of tidal current while at sea?
  a. The shape of the ocean basin below
  b. The magnitude of gravitational forces and inertia
  c. The position of the amphidromic point
  d. All of these choices

[yasmina]

Answer to Question 1

ANS: A
In mixed tide coastlines, the average of the lowest low tides is taken to determine datum points. This is
important because the mixed tides have two low tides of varying height. Information can be found in
the section The Dynamic Theory of Tides Adds Fluid Motion Dynamics to the Equilibrium

Answer to Question 2

ANS: D
The velocity of tidal currents is less in the open sea because it is not as confined as it is closer to shores
and harbors. They tend to decrease in velocity with depth in the open ocean. Information can be found
in the section The Dynamic Theory of Tides Adds Fluid Motion Dynamics to the Equilibrium.

[abarnes]

Both answers were spot on, thank you once again

[yasmina]

Great! Please up vote