As per Peanut, I'm a strong swimmer and may well have considered I could handle the situation. Though I do have a fair idea, and some experience, re fast moving cold water. Sadly he may well still have had a chance after jumping in, but only if trying to save himself. If he avoided gasping at the intial shock and wasn't hit by anything or tangled up with anything. But he'd have had to immediately abandon all thoughts of rescue and strive to save himself only.
A lot of ifs there and no-one will ever know, but still nothing that warrants some of the callous comments received here. We've all made split second decisions that weren't the wisest, and most probably for a lot less reason than this couple.