Lake Clarity and Cleanliness
While pretty much every lake in Northern Wisconsin is going to look beautiful as the fog lifts off in the morning or the sun sets over it at night, what you see during the day will vary depending on the clarity and cleanliness of the lake. If you are boating on a clear lake you will see a bright white wake behind you and be able to look down through the water around you. When you jump in the water you'll come out feeling clean and refreshed. Clear lakes are usually very clean.
Runoff is the main thing that leads to dirty water and murky lakes generally have a lot of run off, where clear lakes don't. While swimming is always going to feel more refreshing when you are in a clean lake and clear lake, you will always catch more fish in a murky lake. While there are more fish in murky water, the number of trophy sized fish go up as the water becomes cleaner. If the main reason you want a place on a lake is because you want to fish, you are better off seeking murkier water. Keep in mind that murky water is by no means bad water. You can see down up to 7 feet in a murky lake so in almost every case a murky lake can be used just like a clear lake, the "feeling" is just different.
One last thing to consider in regards to lake clarity and cleanliness is color. We have a lot of swamps in Northern Wisconsin. The swamps stain or tan the water giving it a thick red/brown color. When this water runs off and mixes with the water in lakes, the lakes can take on the color. The color doesn't affect the clarity of the lake, but it does change the look of the water. Most lakes have a small period of tanned water in the spring, but lakes with high volumes of water (deep) quickly lose the color. The shallow lakes and river drainage lakes stay that color all year.