"Like dissolves like"
Water is a polar solvent, whereas both cyclohexene and cyclohexane are non-polar solvents.
They are not alike. So when they mix, they are not miscible with one another i.e. they do not form a homogenous mix. They are immiscible.
Therefore, one will form a floating layer on top of the other as a function of density, depending on which is present in the greatest volume.
This occurs because the polar water molecules do not have any inter-molecular interactions with the non-polar of cyclohexane/cyclohexene molecules.