Most effective method of animating non-humanoid characters?

In the game I'm working on, we have a boat. Right now we are working on getting the boat to move and sink depending on how crates are placed onto the boat.

After reading through various tutorials, it seems like most animations are done with human-type characters. What's the best way to animate objects?

These are all 3D objects.

 

There's no real reason you can't use 3 spring joints (left, right, middle) - and suspend the boat. with the right settings, it should act naturally buoyant, and sink depending on weights from crates.

Might need to set the boat to limit itself to z axis rotation or such if it's 3D physics you're using. Also, might not even need the middle spring.

You'll want to start with 2 spring joints and move on from there with testing values until it feels just right.