I have managed to overcome my initial trepidation about getting back into the pool after last year's CA.
I have been doing 3 x 45 min sessions a week since August, and with the weight loss since my previous swimming incarnation I am actually swimming quicker(although still slow). I am now able to breathe bi-laterally for a full 2k session(breathing every 3rd stroke) - I am finding that my upper body(in particular the shoulders, triceps and lats) has got stronger, and I am feeling the benefits on the rower as my rowing is rather upper-body centric already.
I have also discovered the joys of long-distance walking(initially to start getting fit again with a low-impact gentle-ish exercise, and not being allowed to drive for 6 months because of having a defibrillator fitted

I have joined the LDWA(Long Distance Walkers Association) and have done the Round IOW walk in 3 days twice in the last month - the first time was on my own, the second time with a bunch of like-minded lunatics from the LDWA!! - the distance when including daily transfers to and from bus stops is somewhere between 120 and 130 km, so roughly an FM a day.
This walking has really strengthened my legs(and increased my bloody-mindedness) - both gains manifesting themselves nicely into a better rowing experience.
Paul G