CHARACTERISTIC ANALYSIS OF SEA WAVES USING WINDWAVE-12 SOFTWARE (CASE STUDY: MENTAWAI ISLANDS). Territorial water of Mentawai Islands that directly facing to India Ocean has some potency of big waves to happen it has an impact on community activity like fisherman activity, ship crossing and many more. This research is implemented to get the ideas of the characteristic sea waves using with data that are used from December 2016 until November 2017. From processing data of Windwaves-12 can be concluded that the highest significant wave value occurs during the western season (December -February) and east season (June -August) with height 0,5 -2m. In the transition season II (September -November) significant wave height with 0,5 -2 and the transition season I (Marchmay) lowest significant wave in 0,5 -1,25 m until this season still in the safe situation for the people to do their activity.