Alistair Grim's Odd Aquaticum

With evil Prince Nightshade hot on their trail, Alastair Grim and his apprentice Grubb and the rest of the crew of the unique mechanical/magical apparatus known as the Odditorium embark on a perilous underwater adventure to the otherworldly realm of Avalon, to find the legendary sword Excalibur, the only weapon capable of penetrating the prince's magical suit of armor.