Bottom fishing means that even if the price drops, you are still optimistic about the concept and are willing to buy at a price that no one wants.
Most people are scared when they bottom fish. They buy it, and then they start to panic when it drops again. This proves that they are not optimistic about the target, so don't bottom fish.
Bottom fishing means that the project has fallen to the point where everyone hates it, but you are still willing to buy it at that price. This means that you are strongly optimistic about the project. You must have confidence in yourself, and this confidence is not given by others.