From and RPGnet Forum thread on adventures based on titles alone:
Into The Leviathan's Maw
1492 AD, and Spain's fortunes rest on the success of Christopher Columbus. But rival kingdoms seek to crush this new empire before it begins, and one is backed by forces from out of time and space.
A group of time travellers arriving in Palos de la Frontera to see the fleet off are caught up in the panic when another ship hits the shore, a wreck guided in by a single crewman who babbles about "a monster 'neath the waves, longer than the ship itself!"
Examining the wreckage confirms that something large and powerful smashed the ship up, from below and to the side. Something is indeed targeting ships leaving the port - something not of this time or place.
Investigation points to an alien signalling device calling to and controlling a prehistoric sea monster, being used somewhere in the port. João II of Portugal has sent agents to wreck the Spanish plans, backed by three hooded figures who call themselves the Forgotten, wielding futuristic technology and set on destroying Columbus's fleet. With the ships sailing at dawn, the travellers have just a few hours to solve the mystery and stop the plan. They may have to stow away on one of the most important voyages in history to head off the Leviathan's attack...
Things To Do: Fend off the Leviathan and prevent the catastrophic alteration of history.
Antagonists: The Forgotten, Spanish troops and Portuguese agents, pirates, the Leviathan itself. Possibly a special guest appearance by the Spanish Inquisition if you think your group can resist Monty Python references.
Action Scenes: Being chased by guards, stopping assassinations, stowing away on the Santa Maria in order to ward off the Leviathan when it attacks.
Problems: There's really no way most groups can fight a gigantic sea monster, so the ability to call the Leviathan and therefore send it away will have to be available to them. This means getting into the Forgotten stronghold and using the device. Alternatively, a more hands-on group might prefer something they can fight directly - like replacing the Leviathan with an army of Sea Devils invading the port.
Things To Prepare For: There are several sides to the conflict, both mundane and unearthly. Maps could be useful for the port, and deck plans for Columbus's fleet.
Continuing the Adventure: What else are the Forgotten planning, and why? There are pivot points throughout history where they could wreak havoc and undo human development.
(Grrr. Nobody ever did write Terror Of The Screaming Skulls.)