At a quick glance, it appears that Dogen has been killed at the hands of Sayid. However, there are several questions that have risen from this action.

For one, in the previous episode 'The Lighthouse' It appears that Jacob is pouring something into the water. If you look at the picture, it appears that he is pouring some kind of ash into the water. One could argue that this may be some kind of substance that is used to 'purify' the water, meaning that Dogen and the interpreter may come back to life.

In addition being that Dogen was drowned in the water similar to how Sayid was, one can logically conclude it might result in a similar outcome to Sayid's case.

None of this is certain however, and it may be possible that Dogen is truly dead. We will have to wait for the next episodes to be released to know for certain.