Abstract
According to the long-term observed records of oceanography and meteorology around Japan, the direction of seas is the same as that of wind and even in the case of swells this is true. The reason is that the wind force is very strong, and generate seas and unifies swells almost instantaneously. Sea state becomes mostly complicated when the following condition is satisfied, namely (H/T)_<seas>=(H/T)_<swells>, in which H is wave height and T is wave period.
