na·ta·to·ri·al 
(nā′tə-tôrē-əl, năt′ə-) also na·ta·to·ry (nātə-tôr′ē, nătə-)
(nā′tə-tôrē-əl, năt′ə-) also na·ta·to·ry (nātə-tôr′ē, nătə-)adj.
Of, relating to, adapted for, or characterized by swimming: a natatorial appendage; natatorial birds.
[From Late Latin natātōrius, from Latin natātor, swimmer, from natātus, past participle of natāre, frequentative of nāre, to swim; see snā- in the Appendix of Indo-European roots.]