Inspecting an object in your inventory by alt-clicking it while hopping between two boats in the middle of the ocean then right clicking a boat to inspect it will cause you to die.
Golly, that's complicated, Here's a video about it too:
Also, you can use this while jumping into a boat from land to "walk on water" and place ocean structures extremely close to land, That's another can of worms on its own.
If there's a way to stop players from cancelling that animation, that would be an easy fix for tons of related bugs.
Oh yeah, and completely preventing players from placing "ocean structures" while not in a boat would be another easy fix for ocean structure placement exploits.
Steps to Reproduce
1. Place 2 boats in the middle of the ocean 2. Jump from boat A to boat B. 3. Inspect an item in your inventory by alt-clicking it while the animation is playing. 4. "Inspect" a boat by right clicking it. 5. Die. (sorry)
This issue has not been confirmed by a developer yet.