How do piers connect networks through a lake?

[kcigam]

Does anyone know why the longest railroad in this game is the 7-pointer on the right, and not one that starts on the center-left and goes through the river to connect with the other railroad on the bottom-left?

The length of this railroad is 9, AFAICT. Am I misunderstanding how piers connect networks?

https://imgur.com/a/cSDUxB7

[Marja1991]

The longest railroad needs to be continuous. There is water between the tracks of railroad, so those are not continuous. Piers connect to everything else connected to the lake, but you need to be able to follow the railroad/highway all the way without interruption.