In 1976, diver Jose Roberto Texeira salvaged two intact amphorae from the bottom of Guanabara Bay, 15 kilometers from Rio de Janeiro. Six years later, archeologist Robert Marx found thousands of pottery fragments in the same locality, including 200 necks from amphorae.
Amphorae are tall storage vessels that were used widely throughout ancient Europe. These particular amphorae are of Roman manufacture, circa the second century B.C. Much controversy erupted around the finds because Spain and Portugal both claim to have discovered Brazil around 1500 A.D. Roman artifacts were distinctly unwelcome. More objectively, the thought of an ancient Roman crossing of the Atlantic is not so farfetched. Roman wrecks have been discovered in the Azores; and the shortest way across the Atlantic is from Africa to Brazil -- only 18 days using modern sailing vessels.
(Sheckley, Robert; "Romans in Rio," Omni, 5:43, June 1983.)
Here's the introductory portion of the text from the second link:
Two thousand years ago, the most valuable commodity “known to man” was salt. This is because most fresh meats and fish were preserved by packing in salt. In fact, salt was so valuable, it was used in place of coinage. This is where the word “salary” emerged (as well as the expression “he’s not worth his salt”). The Romans had a large salt production facility on Ilha do Sal (Salt Island) in the Cape Verde Islands, which are 350 miles off the coast of West Africa. This location is directly in the path of the hot, dry winds of the Sahara Desert, which can easily blow 60 knots from the east. It is believed that this Roman merchant vessel was heading for Salt Island to pick up a load of salt and to provision the local army garrison when a fierce Sahara storm started. Roman ships were clumsy by modem standards and would have no choice but to lower their sails and to run with the winds to avoid capsizing. The Sahara winds can blow for many days and the Salt Ship was carried to Guanabara Bay (near Rio de Janeiro) in Brazil. In the middle of the - Bay is a large submerged rock lying 3’ below the surface called Xareu Rock (named after a local fish that congregates here). The ship appears to have been travelling at a high rate of speed when she struck the rock. She broke into two pieces and settled in 75’ of water near the base of the rock. ...
It seems the Brazilian government is not keen on authenticating this as the Italian consulate claims since the Romans were the first to "discover" Brazil, then all Italian immigrants should be granted immediate citizenship !
That story has been blowing around for a few decades. Unfortunately no shard or amphora were ever tested for age, an expert dated the amphora by styling to 3 AD but its not known where the sample came from, nor was a in situ excavation made, nor a paper presented. Some points
They used amphora up until the 17th century (barrels are expensive) in Portuguese and Spanish ships for the transport of Olive oil and wine.
Ships from that area often used river stones to ballast the ship, the river stones were often dug up near the port and were often full of shards-centuries of shards.
The placing of European Amphora for a hoax is always possible as no vessel was found. Although a Roman ship might have made such a crossing it would seem it had no lasting effect on natives, Rome or other civilizations.
The story remains an interesting story that keeps resurfacing year after year. Unless a excavation is done it remains an unconfirmed story.