Go for it I reckon Daz. I've been free of back injury, or even back pain since I quit jogging, and through consistent swimming I've also been able to maintain weight for the last five years or so that's probably about 10-15kg less than my average weight for the preceding five years.
It also does wonders for my mood. A decent set of laps leaves my whole body feeling both used and relaxed, and my core temperature elevates less which is damn handy in the tropical heat.
Having a really convenient local pool has been pretty key to me sustaining the habit both in Fremantle and up north, but other than that it's an easy choice.