Hourly time series at seven locations throughout the southern Gulf of Mexico were used to calculate the trend and the inter-annual sea level. The sea level series from January 1966 to December 1976 were filtered using a Lanczos low pass filter to remove oscillations with periods smaller than one year. The results revealed a sea level increment of about 1.4 mm yr-1 from 1966 to 1976 in the southern Gulf of Mexico. The monthly sea level variability obtained after the trends were removed, presented a sea level setup during winter and a sea level depression in summer attributed to seasonal wind conditions. The horizontal representation of averaged sea level in the southern Gulf of Mexico presented a saddle critical point. The associated sea level slope indicated water accumulation at Ciudad Madero in the western side of the gulf and Coatzacoalcos in the southernmost station, and sea level depressions at Tuxpan and Progreso in the southwestern and southeastern side of the gulf, respectively. Nevertheless, one of the most intriguing result is the presence of a Kelvin wave with a two mode oscillation axis that goes from Progreso to Tuxpan.