In my experience, my tinc species prefer to lay under coco-huts. I usually place a clean petri dish, or plastic container lid under the hut so that I can easily remove the eggs. I have also had tincs lay on a sturdy magnolia leaf.
I have seen several species of my frogs go to the water immediately after laying eggs, but it is not normal for frogs to sit in the water dish on a regular basis. It could be an indication of illness. If your cobalts are truly courting, you may want to look around for eggs laid on a rock, large leaf, or other damp, but solid surface within the tank. If they have been courting for a while, it could be that they laid eggs, the tadpoles have hatched and they are transporting to your water, in which case, you will see tadpoles in the water.
If you plan on them raising their own tadpoles, then make sure you have a significant amount of water with an oak leaf or two in the water dish.
Thanks! The female laid 5 eggs a few days before they were shipped to me but all the eggs were bad. I have only had them for 2 weeks. I have a coco hut with a lid under it. They don't always sit in the water dish. I see them both at different times in the hut but have not seen them in there together. The male is out and about most of the time but the female hides.
My cobalts always lay under a coco hut. I do have a small water feature and they like to sit in the pond ( 1/2 inch deep). I do find that they will not sit in it for long periods then I will see them in there all the time for awhile.