The bireme and trireme were ancient Greek vessels defined by their numbers of rows of oarsmen - two for biremes, three for triremes. There were some less common variants with more, and more, and more rows of oarsmen, for bigger and more impressive ships. One gets the sense that it got a bit excessive after a point...
Tessarakonteres (Greek: τεσσαρακοντήρης, "forty-rowed"), or simply "forty", was a very large catamaran galley reportedly built in the Hellenistic period by Ptolemy IV Philopator of Egypt. It was described by a number of ancient sources, including a lost work by Callixenus of Rhodes and surviving texts by Athenaeus and Plutarch. According to these descriptions, supported by modern research by Lionel Casson, the enormous size of the vessel made it impractical and it was built only as a prestige vessel, rather than an effective warship. The name "forty" refers not to the number of oars, but to the number of rowers on each vertical "column" of oars that propelled it, and at the size described it would have been the largest ship constructed in antiquity, and probably the largest human-powered vessel ever built.
