Foundation casting of a house
Concrete for the foundation base (aka footing) poured into mud and standing water will not cure properly will be not suitable for use as a footing. You would be well to do one of:


Wait for the water to evaporate and/or soak into the ground.
Pump out the water.
Dig an additional trench away from the low end to drain the water away from the footing area. 


Then let the soil base dry out. You will have to remove the area of the footing with the punky concrete and re-pour it in proper conditions. All this needs to be done before you start building a foundation on top of the footing.