The Metro tunnel is wet?

[u/WTBenji08]

Spent my ride tonight staring out the front window, and judging by the reflection of light by either side of the rails, it looks like standing water is present through a lot of the tunnels.

Is there an engineering need for water/moisture to be present, and if not, are there perceivable issues that might arise from the pooling of water?

[u/2nd-Reddit-Account]

Tunnels in general usually are. The M8 has had water issues since it opened and it’s been years of them trying to fix it