The Collaborative International Dictionary of English v.0.48:

Nauheim bath \Nauheim bath\, etc.
   [Webster 1913 Suppl.] naumachia \naumachia\ n.
   Same as naumachy.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

naumachia
    n 1: a naval spectacle; a mock sea battle put on by the ancient
         Romans [syn: naumachy, naumachia]