Video report by ITV News Washington Correspondent Robert Moore, in the Bahamas
Hurricane Dorian has caused extensive flooding as it howled over low-lying islands off North Carolina.
With winds down to 90mph, the category one hurricane lashed homes and businesses with wind, rain and floodwaters as the storm's centre passed just off the islands.
The floods hit the US state as the Royal Navy were drafted in to help with the challenging conditions faced by survivors in the Bahamas.
The Coast Guard began landing aircraft on Ocracoke Island to drop off local law enforcement officers and evacuate a resident in need of medical care.
Authorities told people to get to the highest point in their homes as they waited to be rescued.
"It's bad," Ann Warner, who owns Howard's Pub on the island, said by telephone.
"The water came up to the inside of our bottom floor, which has never had water."
"We're safe," Ms Warner added. "But it's certainly a mess."
Another Ocracoke Island resident, bookshop owner Leslie Lanier, texted: "We are flooding like crazy. It is in the houses, and there will be more before it stops."
"Lots of people are getting water starting in their homes," Ms Lanier added. "I have been here 32 years and not seen this."
The Hyde County Sheriff's Office said deputies, medics and other rescuers were also heading to the island amid reports of "catastrophic flooding".
"There is significant concern about hundreds of people trapped on Ocracoke Island," Governor Roy Cooper said.
He said that the water was rising fast and that authorities were telling people to get to the highest point in their homes. Even in good weather, the island is reachable only by boat or air.
Dorian is expected to remain a hurricane as it sweeps up the Eastern Seaboard on Friday and Saturday, far enough offshore that its hurricane-force winds are unlikely to reach land.
More than 370,000 people were without electricity in the Carolinas and Virginia as Dorian moved up the coast.
At least four people were killed in the south east. All were men in Florida or North Carolina who died in falls or by electrocution while trimming trees, putting up storm shutters or otherwise getting ready for the hurricane.
On the Outer Banks, forecasters said large and destructive waves could reach nearly to the ceilings of one-story structures along the 200-mile string of islands.
"Do not let your guard down," Dare County emergency managers warned people who insisted on riding out the storm.
As Dorian closed in, many people on the Outer Banks tied down their boats, removed objects from their yards that could blow away, and hunkered down. Ms Warner said about half the 1,000 residents of Ocracoke stuck it out.
At the start of the week, Dorian slammed the Bahamas with 185mph winds, killing at least 30 people and obliterating countless homes.
From there, it swept past Florida and Georgia at a relatively safe distance, then sideswiped the Carolinas on Thursday, spinning off tornadoes that peeled away roofs and flipped recreational vehicles.
Dorian aftermath in the Bahamas
UK experts and the Royal Navy are working in "challenging" conditions to deliver food and other vital supplies in the wake of Hurricane Dorian in the Bahamas, with hopes for rapid improvement in the situation in the coming days.
The Royal Navy has deployed extra medics and is sending another ship to deliver humanitarian assistance to the Bahamas following Hurricane Dorian, the Ministry of Defence has said.
A statement said: "The Royal Navy has deployed extra medics to join Royal Fleet Auxiliary ship Mounts Bay in delivering humanitarian assistance to the Bahamas following Hurricane Dorian.
"A team of 18 military medical staff will arrive in the region this evening and will provide emergency care, surgery and intensive care to those in need."
At least 43 people were killed, with fears the death toll could rise, after the storm battered the Abaco and Grand Bahama islands with winds of up to 185mph winds and lashing rain.
The roofs of homes were ripped off, roads damaged and debris left floating in brown floodwater, with one local relief worker describing "apocalyptic" scenes.
The British Government has pledged £1.5 million to help deliver aid, saying it is estimated that several hundred British nationals live in the worst affected areas of the Bahamas.
The Foreign Office said it is working to establish how badly they have been affected and deploying staff and members of the British Red Cross for "emotional and practical support".
A Royal Navy helicopter rescued three children, and a British person who was trapped beneath rubble for several days after the hurricane.
The Wildcat helicopter, operating from Royal Fleet Auxiliary ship Mounts Bay - which has been stationed in the Caribbean since June in readiness for hurricane season, was flying over Great Abaco Island to assess the damage when its crew were called to rescue a casualty from Elbow Cay.
The crew pulled the person from the rubble and took them back to Mounts Bay to be given emergency medication before being airlifted to the capital Nassau.
The Royal Navy said that the Wildcat also rescued a woman, her two children and a baby, and took them to Nassau.
The Navy has so far provided emergency shelter and hygiene kits for hundreds of people, more than 8,000 bottles of water and hundreds of days' worth of food.
The ship is also using an onboard system to turn sea water into drinking water to help an estimated 62,700 people across the Bahamas who need access to clean water.
A team of five humanitarian experts from the Department for International Development (DFID) arrived in Nassau this week to work alongside the Bahamas Government's National Emergency Management Association (NEMA) and the Caribbean Disaster Emergency Management Agency (CDEMA).
Head of the UK team, Jon Stone, said on Friday: "The clearance process is still going. There are roads that are damaged. We expect it to change rapidly over the next couple of days but it is still a challenging situation."
Foreign Secretary Dominic Raab said: "Hurricane Dorian has devastated lives and communities in The Bahamas.
"The Foreign Office is co-ordinating the UK's cross government response so that we get aid and support to those who need it most."
International Development Secretary Alok Sharma said: "DFID experts are working as part of the cross Government team alongside local authorities, the British military and international partners to urgently get life-saving assistance to the people of the Bahamas."
Anyone worried about a loved one in the Bahamas who may need UK consular help can call 0207 008 1500.
The Foreign Office has advised against all travel to Grand Bahama and the Abaco Islands due to the impact of the hurricane.