Good morning, translatorcz,
It would appear that there were three people paddling about in single kayaks like these
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"Stay back" means two, (Liebl and I), remained where they were and watched the fellow named Kingman struggle against the wind and large waves. He is able to go 50 yards (towards the shore? That's not clear.) before giving up and returning to the other two kayakers.
It's a very nice scene.
Joe