Chung Hom Kok Cave/Tunnel [????- ]

A very interesting cave/tunnel (marked on local hiking maps/OSM map). Right below and to the east of DEL2. At first sight it appeared to be a natural cave carved out by the ocean, but upon entrance and inspection I have a feeling it could be man made or a combination of the two. Anyone who knows about this stuff is welcome to comment, but for me there were a few features that made it seem not completely natural.

-I accessed the cave easily just an hour after high tide. No waves even within 20 meters of the entrance. Additionally, the cave had a number of mosquitos which would insinuate fresh water stagnating. These facts mean that (at least for the past while) the cave has not been subject to the ocean, so it makes me think how the ocean carved it out so well.

-The tunnel is very jagged and the inner frame (shown in a photo attached) is very reminisent of a man made (Japanese style) tunnel frame. It is perfect for a person to enter.

-Finally, after this frame it opens up into a huge cavern with high ceilings. This seems odd considering how much smaller the first section was.

I might be completely mistaken here but those things stood out to me.

l Accessed from a rope on DEL2 to the rocks below. Between two rocks there is a large cut and the tunnel/cave is at the back of it.