Phaselus ille, quem videtis, hospites,
ait fuisse navium celerrimus,
neque ullus natantis impetum trabis
nequisse praeterire, sive palmulis
opus foret volare sive linteo.
(from: http://rudy.negenborn.net/catullus/text2/l4.htm )
The general meaning seems clear enough.
This phaselus, which you see, guests, says it was the swiftest of ships, and was not unable to surpass the speed of a floating rafter whether it was necessary to fly with oarblades or sail.