RYA Day Skipper Tides and Tidal Streams

Question 1

What causes spring tides?

Accepted Answer

The gravitational pull of the sun and moon acting in alignment (at new and full moon)

Answer

The spring season

Answer

Strong winds from the west

Answer

The Earth's rotation speeding up

Question 2

What is the 'Rule of Twelfths' used for?

Accepted Answer

Estimating the rise or fall of tide during each hour of a roughly six-hour tidal cycle

Answer

Calculating boat speed

Answer

Measuring wind speed

Answer

Calculating fuel consumption

Question 3

What is 'chart datum' in relation to tides?

Accepted Answer

The reference level on a chart below which depths are shown and above which tidal heights are measured

Answer

The average sea level

Answer

The highest tide level

Answer

The depth at which anchoring is safe

Question 4

What is the difference between 'height of tide' and 'depth of water'?

Accepted Answer

Height of tide is the vertical distance from chart datum to the water surface; depth of water is chart depth plus height of tide

Answer

They are the same

Answer

Height of tide is always greater

Answer

Depth of water is measured from the surface down

Question 5

What is the approximate interval between successive high waters at a given location?

Accepted Answer

12 hours 25 minutes

Answer

6 hours

Answer

24 hours

Answer

8 hours

Question 6

What does 'neap tides' refer to?

Accepted Answer

Tides with the smallest range, occurring when the sun and moon are at right angles to each other (first and last quarter moon)

Answer

The largest tidal range

Answer

Tides caused by storms

Answer

Tides that only occur in estuaries