Thanks for your replies everyone. One aspect that hasn't come up is nutrition. My wife and I were vegetarians for about 10 years back in the 1980's. I thrived on it (type A blood). My wife (type O) did OK but every now and then would kill for a steak. Those were my distance running years. We have gradually evolved to a fish, poultry and lots of fruits and vegetable nutritional diet. We are happy with this.
In the supplement area I have used a protein smoothie that gives me about 30gm of Pr about half hour before swimming and another one after the swim session. I add 5gms of Creatine monohydrate to the post swim drink for 30 days on and 30 days off. Also add flax oil and hemp oil and ground up sesame, pumpkin and sunflower seeds to the second drink. Also a daily vitamin and mineral tablet and that's it.
Any comments about advisability or additions to this regime. Don't be scared. I will read them with an open mind.
May we swim with ease at the speeds we choose.