Blue Lagoon is a long established flood relief lake created by the widening of the old arm of the River Nene. Restricted water flows through the lake make it susceptible to serious weed problems during the Summer. The fishery also includes the “Dead Arm”, which is the old course of the River Nene from near the Bedford Road roundabout to its confluence with the “new” course of the river at Midsummer Meadow. The fishery also includes the “old arm” of the river from the Rushmere Road bridge upstream to the lock near Abington Mill.