Check out our wiki page on how to map straits. https://wiki.openstreetmap.org/wiki/Tag:natural%3Dstrait. Using a node is preferred because the start and end of the strait is hard to determine. 

Also, I'm unable to find any reference to the Segastill Passage. Where did that name come from? I'll send you more info on OSM in a message.
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            Published using OSMCha: https://osmcha.org/changesets/167449711
            