Table I

Seaman’s Term

Sea Condition

Typical
Wave
Height
Feet

Typical
Condition
Attainment
Time

0

0-1

0-1.7

Calm

Glassy-smooth, mirror-like  

Smooth

- -

1

2-3

1.8-4.0

Light air

Scale-like ripples

Ripples

1-10 min

2

4-6

4.1-7.4

Light breeze

Small, short wavelets with glassy crests

1/3

5-15 min

3

7-10

7.5-12.0

Gentle breeze

Large wavelets, crests begin to break, occasional form

1-2

5-20 min

4

11-16

12.1-18.9

Moderate breeze

Small waves, some whitecaps, more frequent form

2-3

15-60 min

5

17-21

19.0-24.7

Fresh breeze

Moderate longer waves, better formed, many whitecaps, much foam, some spray

3-4

15-60 min

6

22-27

24.8-31.6

Strong breeze

Large waves form, many whitecaps, foam everywhere, more spray

4-5

1/4-2 hr.

7

28-33

31.7-38.5

Moderate gale

Sea heaps up, streaks of foam spindrift begins

5-6

1/2-3 hr.

8

34-40

38.6-46.6

Fresh gale

Moderately-high long waves, crests into spindrift, well-marked streaks of foam

6-7

1/2-3 hr.

9

41-47

46.7-53.9

Strong gale

High waves, sea rolls, dense streaks, spray affects visibility

7-9

1/2-4 hr.