In any case not otherwise provided for in this subchapter, the Secretary shall be prohibited from condemning any commercial property used for commercial purposes in existence on December 31, 1964, so long as, in his opinion, the use thereof would further the purpose of this subchapter, and such use does not impair the usefulness and attractiveness of the area designated for inclusion in the lakeshore. The following uses, among others, shall be considered to be uses compatible with the purposes of this subchapter: Commercial farms, orchards, motels, rental cottages, camps, craft and art studios, marinas, medical, legal, architectural, and other such professional offices, and tree farms.
(