Firstly, I must disagree partially to fnordian about strength training (weightlifting) in relation to cardiovascular workouts. One may have better form in the weight lifting if you do the cardio workout after the lifting. However, if one performs the weight lifting first and does something, such as swimming, one will find themselves unable to move very well! In the case of swimming, this can be extremely detrimental to such things as stroke (or form, in the case of swimming) and confidence in oneself. I myself would suggest a quarter to half cardio before the lifting part of the workout, and than finishing up with that.

Secondly, I have heard many arguments about dehydration in relation to swimming. Neophyte swimmers often feel that since their workout is in water they will not dehydrate. But, they often forget about the substance that turns hair green, or chlorine, along with whatever other substances may be present in the water. These substances will leech the swimmer of liquids and will cause the body to close pores to incoming substances, while still allowing sweat to pump out. This will lead the swimmer to dehydration. This is something to be watched out for by coaches especially, making sure that if one of the swimmers does have an intake of fluid during the workout, moderatly as not to cause cramps.