The Royal Navy has begun a review of the circumstances leading to the capture of 15 of its personnel by Iran.
The crew returned to the UK on Thursday after 13 days in captivity
Rules of engagement, equipment and procedures will all be analysed, the Ministry of Defence said.
The head of the navy, First Sea Lord Admiral Sir Jonathon Band, defended both British operations in the Gulf and the actions of the captured crew.
The 15 were held in Iran for 13 days. Iran claimed they had strayed into its waters, which the UK denied.
Sir Jonathon told BBC Radio 4's Today programme: "This incident was a most extraordinary act conducted in those waters. I think our people have reacted extremely well in very difficult circumstances."
He added: "The boarding operations taking place that morning in the northern Gulf were sanctioned by the United Nations under specific resolutions.
The crew were stationed aboard HMS Cornwall
"They were being conducted under operational procedures with the coalition of US, UK and Australian forces."
Sir Jonathon said UK boarding operations had stopped for the time being but coalition operations were continuing under British command.
The MoD said that the UK would continue to ask Iran to return its two captured boats used by the 15 sailors and marines, but he held out little hope of success.
The freed personnel were helicoptered to the Royal Marine base at Chivenor in north Devon on Thursday, after arriving on a British Airways plane at Heathrow in London.
Earlier, they spoke of their happiness at being back in the UK and reunited with relatives.
One of the captured crew, Lt Felix Carman, said the group had been "completely overwhelmed" by the goodwill they received when they arrived back at Chivenor.
CAPTURED NAVY PERSONNEL
Chris Air, 25, from Altrincham in Cheshire
Mark Banks, 24, of Lowestoft, Suffolk
Paul Barton, of Southport, Merseyside
Arthur Batchelor, 20, of Plymouth
Felix Carman, 26, of Swansea
Christopher Coe, 31, of Huddersfield
Dean Harris, 24, of Carmarthen, west Wales
Danny Masterton, 26, of Muirkirk, Ayrshire
Adam Sperry, 22, of Wigston, near Leicester
Nathan Summers, of Hayle, Cornwall
Joe Tindell, 21, of south London
Faye Turney, 26, originally from Shropshire
Several said they had been well treated while in Iran, but since their return there have been suggestions some may have been held in solitary confinement.
Lt Col Andy Price, who met the group at the airport, said there had been "times when they were left alone", but refused to go into further detail.
Chief of Defence Staff, Air Chief Marshal Sir Jock Stirrup, said: "They did exactly as they should have done from start to finish... and we're extremely proud of them."
Penny Banks, who was reunited with her son, Lance Corporal Mark Banks, said: "We are delighted to have him back - it was nice to hold him again."
In a press conference outside Downing Street, Tony Blair said he was "glad" the crew had been returned "safe and unharmed".
He said "no deal" had been done with the Iranians to secure their release, despite claims by Iran that it received a written apology from Britain on Tuesday.
And he contrasted the safe return of the Britons with four soldiers killed in Basra in Iraq on the same day.
The US welcomed Iran's decision to free the servicemen, but said the positive move would not ease tensions over its nuclear programme.
It emerged on Thursday that in a television interview recorded before their capture, one of the crew members, Capt Chris Air, had said one purpose of patrols in the area was to gather intelligence on "any sort of Iranian activity".
In the joint Five News and Sky News interview, recorded on 13 March but not broadcast until after the 15 had been released, he acknowledged that he was operating close to the buffer zone between Iranian and Iraqi waters, adding: "It's good to gather intelligence on the Iranians."
The MoD said this was "all part of modern operations".