Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭper-năto, āre, v. n., to swim above or on top, to float (post-Aug.), Col. 12, 9, 2; Plin. 7, 15, 13, § 65; 28, 9, 35, § 134; App. M. 6, p. 180, 36; Paul. Nol. Carm. 21, 179.
With dat.: arieti (Phryxum), App. M. 6, p. 185, 33.