I heard the coast guard helicopter taking off yesterday on one of those frequencies. I'm going to be camping right on Lake Michigan this weekend and I think I'll be able to hear them better.
Don't forget to program in VHF channel 16, 156.800MHz, the emergency hailing channel. Any boater in distress will be calling the Coast Guard on Channel 16. Depending upon the circumstances, the Coast Guard will then shift the conversation to 21 or 22, whichever is their normal working channel.
The area you are in is covered by Air Station Traverse City the helios are up in the air for most of the day plus you will hear a lot of the Coast Guard Aux doing shorline patrols out of Traverse City ch 21 is very active in this area.