Seven.

This is coolbert:

Seven against Rome?

NOT exactly so!

As described by the title of the Internet article seven famous shipwrecks five of which have a military dimension.

"Sunken Treasures: The Curious Science of 7 Famous Shipwrecks"

Regarding the Swedish naval vessel Vasa now a resurrected museum piece there is this curiosity:

"the Vasa [1628] . . . more of its hull and detailed woodwork have survived the centuries under the sea. Marine archaeologists say the main reason for the Vasa's remarkable state of preservation was the heavily polluted waters of Stockholm's harbor until the 20th century, which created a toxic environment for microorganisms that break down wood"

ALSO THOSE AMERICAN WARSHIPS SUBJECTED TO SHOT BRAVO REMARKABLY STAYING AFLOAT IN A MANNER NOT ANTICIPATED BUT HEAVILY DOUSED BY RADIOACTIVITY THAT COULD NOT BE DECONTAMINATED!

WATER TIGHT DOORS ON THOSE SHIPS SHUT? ALL SHIPS SANS CREW NO DAMAGE CONTROL POSSIBLE.

See here and here You Tube video of Shot Bravo. The latter video in slow-motion.

coolbert.