I've experienced multiple unexpected things with lead rendering when attached to boats. Mainly, they sometimes do not render when closing and reopening a world with boats on leads attached to fences. I also had a strange issue where I had attached a boat to a fence but the lead was still rendering attached to my hand and not the fence, even though it was acting like it was attached to the fence and it didn't break when I moved away from it. I relogged when this happened and none of the leads were rendering anymore.

I don't have any images or clips to prove this one, but I was able to die when falling with a bunch of boats on leads and i was on top of the boats. It was actually really fun, but I somehow died on the boats without even falling. I don't think it's really to do with the leads but, I thought I'd mention it.