From: Winnipeg, MB
Let's recall that there were two types of nets in use at the time - major ports sometimes had nets at the entrance (as Pearl did on Dec 7th), and individual ships could also be surrounded by nets (which was not done at Pearl on Dec 7th).
I have no idea whether the IJN routinely deployed nets around individual ships at anchor, but a net at an entrance to Truk lagoon wouldn't keep a TBF from sticking a torp into an IJN ship at anchor there.
True; the lagoon is like 38 miles wide.
I thought I saw an article saying 100 miles wide, but I suppose that could have been 100 square miles in area. The pictures in the article and accompanying map showed dozens of islands within the lagoon and several anchorages along the perimeter of the lagoon. There were cargo ships all over the place, some in deep water, and warships were scattering trying to find exit passages that were not stalked by bombers. IIRC, one of the Iowa BBs caught a small IJN DD exiting the lagoon and sank it with very long range gunfire.
So the concept of having torpedo bomber strikes at ships in port would have been a good one if it could have accounted for all the shallows and protective nets involved.
No matter how bad a situation is, you can always make it worse. - Chris Hadfield : An Astronaut's Guide To Life On Earth