There is virtually no humidity in Merimbula. Even on a hot day because you are on the coast, you always get cool breezes. I moved from Sydney's Western Suburbs 17 years ago and it was a hot horrible place in summer. We used to have to sleep with the air conditioner on. Now we just open a window and catch a nice sea breeze.
That's also plenty of things to do here, other than fish.
Merimbula has the most temperate climate in Australia. Humidity is generally not a factor. The temperature in summer is warm and the winter days are usually mild but you will have some very cold days when the wind is coming from the west. There are many middle aged people here as well so I am sure you'll make friends, good luck.