Few people know that Torchwood has a miniature submarine. It’s part earth technology, part alien, developed by the institute because the Rift is fickle and doesn’t always drop objects on land. Scuba diving in the bay isn’t always a practical method of retrieval, some areas being quite deep, and besides, travelling by sub is quicker.
Even so, not everyone on the team is qualified to use it. Gwen is claustrophobic, while Tosh will only go down with somebody else.
Ianto loves it though. He may never get to other planets, but he can visit the extraordinary world beneath the sea.