The North Hinder or Noord Hinder lightship on the approach to Flushing is seen by John on the outward unplanned voyage from Harwich in We Didn't Mean to Go to Sea. There is a night drawing of her (WD15):
What was that? Flash, flash in the darkness far ahead …. It must be a lightship. He decides to steer for it (WD15).
At dawn Susan says to John: ...... But we passed the lightship a long time ago (WD16).
"Isn’t it light enough to turn back now" said Susan. "You said we’d go back as soon as it was light, to talk to the people on the lightship" ..... John says "I don’t believe we ought to turn back at all" (WD16).
That lightship must have been the “North Hinder” says Daddy (WD23).