SPOILER WARNING! Walkthrough!!!!! (revised) Ending A: Save the child.---. Ending B: Don't save the child.---. Ending C: Allow the boat to drop mines on you three times.---. Ending D: Allow the sub to hit you with their torpedoes three times.---. Ending E: Destroy the sub. Pass it on
For the C ending don't touch the mines, drown people are anything like that; just wait for it to hit you three times.
Of course make sure you've got all the upgrades on your own tower. Make sure you have 9999 mana when you break down the tower and then start spamming hobbits and create dragons when possible. When your mana is full you can create an angel but give priority to the dragons.