I hadn’t given this much thought but the same must apply to lifeboats. I’ve looked at the stern of a Severn and Tamar class and they have an elongated opening underneath the hand rail but the Shannon is quite different

“Gob eye, used on large anchor handling tugs to prevent girding. Same principle as tow pins in smaller boats,” said Marcel, my tugboat captain friend

A recent post reminded me of a small point regarding this important part of a tug when towing. I believe the tug needs a gog iron attaching to the deck above the prop otherwise there is a risk of the tow pulling the tug over.
Copied this from a Google post to explain further:
"A Gog eye is actually fixed to the deck, in the shape of an eye, (kind of a flattened circle), or in the case of the older tugs, Bits , that were attached to the deck on the stern of the tug. On the tugs that I worked on a tow rope would be let down from the ship and attached to the hook of the tug, we would then use a large diameter rope ( that we called a Kant rope)that would be wound around the capstan through the Gog eye and then attached to the tow rope by means of a very large shackle. the tow line would then be pulled down toward the deck by the capstan so that the centre of gravity would be through the bits (gog eye) and above the prop. It was a lot easier to do than explain. Those days the Tugs were old Empire class and were basically falling to pieces."
I speak from experience as my small tug suffered such a fate whilst towing my MV Mercantic at New Brighton many years ago.
dave976