Beardedbruce posted the following above, "This vessel looks like it was buttoned down tight for winter and it sank," said Schimnowski. "Everything was shut. Even the windows are still intact. If you could lift this boat out of the water, and pump the water out, it would probably float."

If water had entered through the seams as suggested by Teribus, just raising the boat and pumping out the water would not be enough to get it to float.

The Guardian and others say almost all the hatches were closed. So if at least one hatch was open maybe that is where the water came in.

https://www.theguardian.com/world/2016/sep/12/hms-terror-wreck-found-arctic-nearly-170-years-northwest-passage-attempt