Whizbang Dustyboots
Gnometown Hero
Creatures of Freeport is also a very cheap but very good book of aquatic monsters. It follows the Monsternomicon/Wanderers Guild model of providing more information about fewer creatures.
And can I just say that 4E needs to have sea serpents in the MM1? Talk about an iconic monster that has NEVER made it into the core monster book of D&D. We get a dozen or more monsters that intentionally play off expectations about sea serpents (Creatures of Freeport has a not-a-sea-serpent, for instance), but I think only Seas of Blood has actually given us the real deal (dragon-typed sea serpents). Exasperating.
And can I just say that 4E needs to have sea serpents in the MM1? Talk about an iconic monster that has NEVER made it into the core monster book of D&D. We get a dozen or more monsters that intentionally play off expectations about sea serpents (Creatures of Freeport has a not-a-sea-serpent, for instance), but I think only Seas of Blood has actually given us the real deal (dragon-typed sea serpents). Exasperating.