An underlying theme of the cruises aboard the vessels is to compare and contrast Lake Michigan with another water body. Lake Michigan has a surface area of about 22,300 square miles making it the third largest Great Lake. The flushing time of the Lake is 69 years. The average depth of Lake Michigan is 279 feet with a maximum depth of 923 feet, making it the second deepest Great Lake. In contrast, Spring Lake's surface area is about 1,300 acres with inputs of water mainly through springs, streams, and precipitation.
Spring Lake is connected to the Grand River.
Muskegon Lake is 4,149 acres in size and receives flow from the Muskegon River as well as tributaries such as Ryerson and Ruddiman Creeks. Overall water quality can be evaluated by considering the trophic status or biological productivity. Nutrient levels, organic matter content, dissolved oxygen levels, and water transparency indicate the trophic state or biological productivity of a water body. The open waters of Lake Michigan are oligotrophic, and some near-shore areas are mesotrophic. Low nutrient levels, low biomass, high oxygen concentrations, and high transparency characterize oligotrophic lakes.