It was daylight. The Iranian vessels came from Iranian water, 2 miles away. They weren’t “suddenly surrounded”.
There was a journalist on board the ship, Ian Pannell, who said that they had just “boarded a dhow, a traditional Arabian sailing vessel, ... While they were on board, a number of Iranian boats approached the waters in which they were operating – the Royal Navy are insistent that they were operating in Iraqi waters and not Iranian waters – and essentially captured the Royal Navy and Royal Marine personnel at gunpoint.” (Scotsman)
http://righttruth.typepad.com/right_truth/2007/03/iranians_captur.html
Then, there’s the whole matter of the Cornwall watching, with radio contact with them......they could have easily made a stand on the vessel they had boarded, for long enough for help to arrive
From that page “Two boats, each with a crew of six to eight multinational forces, were searching Iraqi and Iranian boats Friday morning in Ras al-Beesha area in the northern entrance of the Arab Gulf, but big Iranian boats came and took the two boats with their crews to the Iranian waters.”
Inflatable boats versus ‘big Iranian Boats’...seems feckless to suggest the James Bond option.