SkiSoloII

Hi guys. I'm sure it's been answered before, but there are so many gps threads, I can't sort them out. I just got a new GPS as noted above. Using for fishing, mostly. Saginaw bay and some inland lakes. What would be the best mapping software for Michigan lake contours? I don't know what maps are the most detailed, or contain the most information. Thanks in advance, Dave Pearson