No not on the same day, because if your bulking your weight training workout should last no longer then 60 minutes, as this is the considered the best time to spend just the right amount of energy into trying to bulk. If you went swimming on the same day you would be burning more calories, less avaiable for use of muscle growth, and if you was swimming for a while on an empty stomach it possible could break down muscle tissue, needed for the extra energy ur needing.
In bulking I recommend that you dont go swimming at all, or only once a week for 30 minutes of swimming.
If you toning its another story, you could go swimming more days of the week and could go on the same day as your weight training, as the more you do cardio the more fat you will burn, remember tho that no cardio session should last no longer then 30 min, because you want just fat breaking down not muscle :] and also u want time for your metabolism to act when not exercising which will still be breaking down fat.
