This trick requires two VMUs. Begin and save a new game using the second VMU. Connect this VMU to the VMU that has your ongoing game. Transfer the food from the new game to the ongoing game. Repeat this as required for unlimited food.
Hold the A and talk into the microphone as clearly as possible to teach your Seaman how to talk. The Gillman stage is the stage when it will first start to say things. Use these words frequently: Hi, Hello, Hey, No, Yes, Seaman, Fish, Fun, Play, etc. Experiment, but do not call it bad things or it will become unhappy.
Set the Dreamcast's system date ahead several days for faster evolution. Be warned that the tank will also not be maintained for that amount of time.
During the game, there will be a shell at the bottom of the tank. Tap the shell until it starts to eat the newborn Seaman (Mushroomer's). After they are all eaten, tap the shell some more until a squid comes out. If you continue tapping, it will die and the Seaman will appear in the next stage of their evolution, Gillman.
After naming your Seaman the first time, you can rename him by repeatedly asking "Do you love me?". Eventually, you will be able to change your Seaman's name.
Press X + R and press Left or Right when over a rock to move it.
Select a Seaman and move the Analog-stick in circles around its head. It should get hypnotized, giggle, and fall backward.
Place the game disc in an audio CD player and play track two to hear a hidden message.