You know what does amaze me.
It's always planes and I have no idea why. Never liners or ferries, which would cause much more spectacle (in that there'd probably be live footage of it gradually going down) and unfortunately, loss of life.
The security checks boarding a ferry are negligible (never been on a cruise liner, probably never will). Also, if you did it in the right place, you could shut down a port or even a shipping lane for weeks.
I hope no terrorists read this.