Don't wear cotton for any reason; the shop that sold you that suit should have explained the options and reasons why, when you got the suit. When cotton gets damp even from sweat you will get cold and could become hypothermic summer or winter at your temps.
Synthetic is the main option. Some people use wool I find it does not work as well as fleece. As said above a poly inside layer to pull moisture away from the body and an out layer for warmth and to hold the moisture, inside the suit underwater its not going anywhere. Some garments with multi layers built in and do this very well. I use a Bare 200 one piece that works summer and winter here in BC.
In summer be careful not to suit up too early and fill your underlay with sweat.
Synthetic is the main option. Some people use wool I find it does not work as well as fleece. As said above a poly inside layer to pull moisture away from the body and an out layer for warmth and to hold the moisture, inside the suit underwater its not going anywhere. Some garments with multi layers built in and do this very well. I use a Bare 200 one piece that works summer and winter here in BC.
In summer be careful not to suit up too early and fill your underlay with sweat.