For the first time in six years a nuclear submarine has docked in Southampton's commercial port.
HMS Tireless arrived into the Solent on Monday morning
HMS Tireless arrived on Monday for a five-day stay.
The Navy now wants to use the port more often and leaflets detailing what to do in the event of an emergency were given to locals before the sub arrived.
Di McDonald, of local campaign group, Solent Coalition Against Nuclear Ships (Scans), criticised the Navy's decision as a risk "not worth taking".
She added: "Risk assessment these days is far different than how it was looked at 20 or even 10 years ago and people want to be kept safe.
"We know there are some risks in life and we have to face those but this isn't one of them - we don't need this here."
But HMS Tireless's chief officer, Commander Iain Breckenridge, said he was not expecting any local opposition.
"It has been many years since a submarine visited the city, but given the help we have received preparing for the visit and the warmth of the people involved, I am in no doubt that the visit will be great fun and thoroughly enjoyable."
"It will show the city and the Royal Navy working together to achieve common goals," he said.
The Trafalgar-class attack submarine has about 130 officers and men and is capable of firing Tomahawk cruise missiles.