Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ūrīnor, āri, v. dep. (ante-class. collat. form ūrīno, āre) [urina; Gr. οὐρέω], to plunge under water, to dive: urinare est mergi in aquam, Varr. L. L. 5, § 126 Müll.; Cic. Fragm. ap. Non. 474, 27; Plin. 11, 37, 72, § 188.
Part.: urinantes, Plin. 9 30, 48, § 91.