The Romans built their first serious fleet in the 1st Punic war against Carthage by copying Carthaginian designs. They defeated the more experienced Carthaginians by using new technology to board the enemy ships and use the excellent heavy Roman infantry against the inferior Carthaginian soldiers and mercenaries.
After the war they reverted back to the more traditional tactics of ramming with a mix of boarding and using shipboard artillery to sink enemy vessels. Rome kept naval dominance from the time of the 1st Punic war until the loss of North Africa to the Vandals hundreds of years later, their only real enemy being the pirates and raiders who tried to pry on Roman shipping while it was undefended.
After the war they reverted back to the more traditional tactics of ramming with a mix of boarding and using shipboard artillery to sink enemy vessels. Rome kept naval dominance from the time of the 1st Punic war until the loss of North Africa to the Vandals hundreds of years later, their only real enemy being the pirates and raiders who tried to pry on Roman shipping while it was undefended.