The reason why it can be watery is when the ladyfingers are soaked for too long and are already soggy when arranged in the baking dish. As the dessert cools, the excess coffee in the ladyfingers will run into the cream and make the dessert watery. My recommendations to either avoid a watery dessert or fix it: 1. Please make sure that you dip them on both sides quickly so that just the outside of the ladyfingers is soft, but the inside is still solid when you arrange them in the pan. 2. If your dessert is watery, you can just try to transfer the Tiramisu to a clean and dry container and remove the excess liquid.