In this tracking the rising tide instructional activity, students use the data in a graph showing the seal level change versus time from 1900 to 2000 to answer 3 questions about the rising tides. Students determine the slope of a line drawn from 1920 to 2000, they find an equation of the straight line in 3 forms and they predict the sea level rises for the years 2050, 2100 and 2150.