When the boat breaks while glitched in a block, it breaks into the old planks and sticks.

How to recreate:
make a long blue ice road which has the blue ice spaced one block apart from each other, make sure you have a little bit of lag, (you might want to turn your render distance up to cause a bit of lag) go full speed ahead until you hit chunks which are struggling to load and keep holding forwards. when the chunk loads you will then keep going or have this glitch happen, if it doesn't happen then the next chunk which isn't loading might make the glitch happen.

How i found this:
I was playing on a quite laggy server which had mob problems and was running at about 10 tps. i had my long blue ice road in the nether (not sure if dimension changes it) and i hit loading chunks, my boat glitched into the blue ice, i was kicked from the boat and then it broke into planks and sticks. (A couple of other people on the server found the same thing happened to them.