ALT Trees on lake shore at the Olin Lake Nature Preserve. At just over 100 acres, Olin Lake is the largest lake in Indiana with an undeveloped shoreline, all of which is protected by this preserve. Most of the shoreline is low and marshy, which contributes to the lack of development. The swamp forest in this area includes tamarack, silver maple, red maple, and green ash. Skunk cabbage abounds in low mucky spots. Aquatic vegetation is sparse because the lake bottom is covered with marl, a white calcareous substance precipitated from the water. On the upland portion of the southeast shore is the remnant of a once-large woods. Many large tulip, oak, and walnut trees were removed in the late 1960s. There are still large specimens of sugar maple, beech, hackberry, and red oak surrounding the stumps of once-larger trees.