The Virgin Group founder survived the disaster by taking shelter in his wine cellar when the hurricane hit his private island.
Seawater penetrated as much as half a kilometre (one-third of a mile) inland in places.
'Catastrophic' storm surge is feared in the Florida Peninsula, where ocean levels were quickly rising.
Pasco County Sheriff's Office warned residents of the 'dangerous side effects' of shooting into the hurricane.
Irma is moving up the western coastline of Florida.
The storm has made landfall in Florida and is expected to move up the western coast.
It comes after two MPs criticised the government's response to the disaster.
Hurricane Andrew left devastation behind in Florida, Irma looks set to be even worse.
Tesla has unlocked the reserved battery capacity in some of its vehicles to help owners get as far as possible.
'Just get out of its way,' US President Donald Trump warned people in Florida.
Evacuees watch nervously on webcams dotted around cities, marinas and beaches.
France's public insurance agency puts huge costs on damage to both island communities.
Around 5.6 million of Florida's residents have been told to evacuate as the hurricane approaches
"I really loved Federal G's first album but thought his more recent one was a little meh," one person tweeted.
Hospitals, factories and warehouses reportedly damaged by first Category 5 storm to hit Cuba in decades.
Government under cross-bench pressure to justify slow response to catastrophe that has battered the Caribbean.
Favourable conditions in the Atlantic are fuelling devastating tropical storms.
Thousands rushing to leave the state, scrambling to load up on fuel and supplies.
Irma's winds of around 175mph (290kph) tore down trees, and flattened homes, schools and hotels, destroying some of the world's most exclusive tourist resorts.
UPS Foundation, Red Cross and CyPhy Works tease one-week drone trial.
Nasa classified Irma as a Category 5 hurricane, Katia as Category 1, while Jose continues to gain strength.
Hurricane Irma, one of the most powerful Atlantic storms in a century, is heading directly towards Florida after it lashed the Caribbean.