Treasure hunters in the US have discovered a huge trove of Spanish gold coins worth $4.5m (£2.9m) off the coast of Florida. The 350 coins found on 30 July come from a fleet of 11 Spanish galleons that sunk in a hurricane 300 years ago while en route from Cuba to Spain.

The pieces were found buried under the sand in shallow waters off Vero Beach. The salvage operation took five days by a three-man crew working for company 1715 Fleet – Queens Jewels, which owns the rights to the wreckage.

William Bartlett, the diver in charge of the operation, refused to disclose what cut he would receive from the discovery. Telling a local newspaper that he dives only as a hobby he said: "I'm just a guy on a boat living the dream."

US state law means that Florida will keep 20% of value of the find. The treasure includes nine rare pieces, known as royal eight escudos, which were being transported to the King of Spain. Only 20 such coins were known to exist in the world prior to this discovery.

The discovery is the second major find by treasure hunters this year. In June, another treasure trove of 50 coins worth about $1m (£600k) was found nearby along the Florida coast.