Why does Stanton watch the submarine base in Holy Loch, and why does he conceal himself on the Keppel? He makes no attempt to stop its progress. He knows what happened on the first voyage, so there is no need for him to find anything out. He makes no direct attack on the submarine. He is not responsible for its crash. If he wants to get to the island, why doesn't he just fly there?
The sudden appearance of the reef and the island in the middle of the ocean is never explained. There is a little discussion that the island may be volcanic and recent, but in that case how come it has soil deep enough for trees to grow, or that the trees have had time enough to grow so big? Furthermore, as it causes the Keppel to be 400 miles off course, it must be enormous.
If the second voyage of the Keppel retraces the steps of the first, what is its course? The first voyage seems to have foundered in the South Atlantic, and the sub ended up off the coast of Ireland. Unlikely, then, that its starting point was Holy Loch, yet that appears to be where the second voyage began.