Hello Mbchiro!
Funny you should mention about the old towels, as we did nearly the same w/ old pieces of tarp that we found nearby, and we used them to keep the tanks cool while we were on our first dive, good idea you have, follow it through! If you have the presence of mind, wet the towels before hand and/ or take some water w/ you, and don’t forget to freeze some water overnight for you guys to drink after the dive, it is a must in that weather. - Seawolf5