Sub-Lt Aaron Barrett, 2IC, Reserve Diving Group Two, talked about what the training involved: “The team of divers will line out along the free area aft of the vessel. That’s the propellers and the rudders.
"They will search that from one side to the other. Then they will line out again and then go... around the bow and then back to the start, having covered the whole hull looking for suspected ordonnance.”
Searching a hull is a perfect training serial - because it is one of the jobs the divers and their regular colleagues are asked to do a lot.
The man in charge, Lt Cdr Nick Foster, Reserve Diving Group, talked about what they were going to be doing: “We’re looking for anything that shouldn’t be there on the ship’s hull… A series of divers on a necklace… basically search two main areas of the ships.”
The dive team moved into position, and three frogmen conducted the search, accompanied by a surface diver.
A reserve diver, coxswain and first-aider stayed on the RHIB.
Despite it being August, it was cold and dank in the corner of the harbour where the search was being carried out.
So, what makes people want to do this?
Lt Cdr Foster said: “People…want to do something that’s slightly more exciting, and more challenging.
"You don’t have to have any diving experience – you can basically come across with no diving skills whatsoever and they’ll teach you.
"All you have to be is reasonably fit and have a willingness to learn basically."
Watching proceedings in Portsmouth was Richard Hanson, a former Royal Marine, now a new Royal Naval Reserve AB2.
He is looking at joining the divers: "There’s a lot about diving that interests me, there’s the actual job itself – the diving itself. It’s working with quite a close-knit team as well."
After about 20 minutes, the mission was complete. The divers headed back to the dive boat to debrief and prepare for further training.
AB1 Angus Robertson, RNR and student, told us what appealed to him about the job:
"It’s something different – how many times do you get to go diving on stuff like this?”
AB1 Mark Armstrong, RNR and fireman said: “It’s something different from a day job. I like diving, so I do enjoy getting in the water and down here with the rest of the lads and getting some diving done.”