Silver Stream's depths
In this chapter
The axe from the mines opens the pit under the bridge; down it, the mines' flooded chamber and the brass cymbals.
Ashore on the near beach and back to Silver Stream. Under the old bridge, the stream runs into a pit covered by a wooden lid. Something sharp is needed, and it's in the mines: leave the coin on the bank, drop down the funnel and go fetch the bridgebuilder's sharp axe from the railway level's far left.

Out of the mines by the minecart (its branch to the far beach), back across the bay, and to the pit under the bridge. Drop the axe on the lid: it opens (Under Silver Stream).
With the aqua lung and the flippers, dive in: the pit's star, and below it the mines' flooded chamber, with three stars and a pair of brass cymbals (A flooded chamber in the mines).
The pit is one-way. Swim out west into the mines, ride the lifts to the minecart and take it to the far beach again, then back across the bay. On Silver Stream's bank, leave the flippers and the aqua lung: no more water ahead. Pick up the coin again.
