These days, fuzzy logic system has widely been applied in many applications, including wave forecasting. In current fuzzy logic development, researchers have started to use interval type 2 fuzzy as a solution to solve the uncertainties problem. The aim of this research is to propose a method to forecast significant wave height by using interval type 2 fuzzy logic. As part of the research, this paper focuses on two objectives; to extend type-1 fuzzy to type-2 fuzzy by assigning uncertainty to its type 1 counterpart and to predict significant wave height for 1 hour, 3 hours, 6 hours, 12 hours and 24 hours lead time. The root mean square error (RMSE) has been used to score the performance of both type 1 and type 2 fuzzy methods. The best result has shown at 6 hours lead time with RMSE of 0.1529. © 2012 IEEE.