sounds like there were 2 inflatable boats with RN soldiers preforming normal operations in Iraqi waters and searched a suspicious vessel. Presumably, they were some distance from their home warship (HMS Cromwell). A number of other vessels (with Iranian Revolutionary Guard types) approached the seized vessel and at gun point took the RN sailors captive.
I've read reports that American military assets were in the area, became aware of the abduction and was ready to respond, but when it became apparent that the RN was going to let this thing play out diplomatically and avoid a shooting situation, the Americans followed suit
IMHO....the defections and seizing of the Qods troops has totally unnerved the Iranians.