Constable Wylie, from the Police Service of Northern Ireland (PSNI) search-and-rescue team, described finding Noah’s body shortly after he and a colleague entered the tunnel chamber which was 8ft (2.4m) in diameter and 10ft (3m) high.
He said they saw human remains and “could clearly see a pair of legs and buttocks” with no clothes.
The witness said he returned above ground to inform his team and two more colleagues joined them when they returned underground.
Wylie said they noticed about half a dozen marks on a thin layer of sludge on the sides of the tunnel and he believed they were finger marks resulting from someone extending their hands out “to steady themselves”.
It was “as if someone was moving through and steadying themselves”.
He also explained that the marks appeared to have been made “by smaller hands”.
“My belief was these marks were made by Noah himself,” Wylie said.
The witness said there was “very little water” in the tunnel at the time.
The inquest was then shown body camera footage used by the police search and rescue team inside the tunnel after Noah’s body was discovered.
There were echoing sounds in the tunnel as well as the sound of splashing and dripping water as the team made their way through the dark environment with the aid of torch lights,
One member of the team remarked, “remains are visible”.
Noah’s body could be seen lying close to a corner in the tunnel.
The search and rescue team also observed that there were “no clothes” and there were “some green deposits on his back”.
Noah’s mother, Fiona, left the courtroom just before the footage was played on screens around the room and she turned four minutes later after the recording ended.