I love these fishy soaps, my kids love them too. They are pretty easy to make but require several steps. Here is how I make mine. I use a retangular bag for this project. Get some clear melt and pour soap which can be found at most craft stores. I like to color the soap green or blue but very pale and I don't add much scent if any at all b/c kids have delicate skin.
So, melt your soap in the microwave add colore. Pour a small layer of soap into the bag, about 2inches. Next, use two clothes pins or clips and clip the bag to a bar of some sort so that the bag at the top stays open it's not bunched but so the soap will stay in a retangular shape. Let cool for about 5 minutes and once it starts getting sloshy you can place your rubber fish halfway into the soap at an angle or how you want. Let soap dry till hard. Once hardened spritz some rubbing alchol on the top layer of the soap. This step is very important for the adhesion of the next layer of soap. Melt your soap again and pour onto the bag soap and over the fish about another 2 inches or so. Hang again as before until completely hardened. Now you have yourself a fishy soap. The kids love to get clean so they can get to the center of that soap and snag the fish.