Wondering what all those lights you see out on the water mean? We've got the answers.

According to NOAA, red lights are used to mark piers and supports.

Green lights generally mark the centerline of the navigable channel under a bridge. If there's more than one navigable channel, the preferred route is marked by three white lights running vertically.

Red lights are also used on some lift bridges to indicate the lift is closed, and green lights to indicate the lift is open.

Double-opening swing bridges are lighted with three lanterns on top of the span so that when viewed from an approaching vessel the swing span when closed will display three red lights, and when open for navigation will display two green lights.

Hope that helps.