How to make driftwood sink

I went to the seaside on Sunday and picked up some driftwood to put in my fish tank.

I went to wash the wood beforehand in my sink and, much to my dismay, the wood floated. In hindsight this seems obvious:

a.) wood floats

b.) it wouldn't wash up on the beach if it didn't float

I felt like a muppet. Anyway, I got on the Googles and found some people mentioned boiling it to make it get soaked with water so it sinks. I boiled it for like 2 hours while playing Monopoly, and at the end just as I was ready to give up, I turned the hob off and put it in some cold water to cool it down. And it sank!

So now there's some driftwood in my tank.