Credit to Zenthisoror of the DCTP spoiler cbox who gives a synopsis of the official Movie 17 website
Also the trailer is on the official website above, if the youtube ones get taken down
The trailer says, "A strange vessels filled with explosives..."
But it then follows it with, "A body without a left arm..." which sounds grim...
The story sounds as though there's a spy on board the Aegis, and they're going to have find him.
Conan says, "If things go on like this, Japan will be in danger!"
Movie 17 Story: A murdered defense force member! A spy on board the Aegis! And the hands of evil getting closer to Ran...
A supremely dangerous emergency mission!
Target: The whole of Japan!
Floating upon seas struck by the early light of morning, was a strange ship, filled with explosives...that ship was the beginning of everything...
Kyoto: Maizuru Bay
Supported by the Defense Force Navy, the valuable Aegis has been opened up for visitors to go on a navy experience cruise.
Conan, Ran, Kogoro and the Detective Boys are enjoying an immensely exciting cruise on the (okay, forgive me the literal translate here. I don't really know much about technology systems in English) electronically weaponized high-tech ship.
Suddenly they hear a loud roar...and an unsettling, uneasy feeling permeates the ship... and not long later, they find a body without a left arm. And it's the body of a defense force member.
They note a number of strange things about the body...
As Conan investigates, they find out that the spy 'X', working for an unspecified country, is aboard the ship.
Who is spy 'X'? And what is his link with the mysterious boat at the start?
The shadow of the creeping spy eventually begins to fall upon Conan and his friends...
A great conspiracy beyond anything imaginable upon the seas, that could rock the whole of Japan, had been hidden away upon the Aegis!
Edit: The ship is called Aegis, and is not the same named missile defense program used by some Self Defense force ships