Apart from the terse writing, that story was somehow more Marvel-like (and by the same token, less Electric Company-like) than I would have expected from that comic. Er, if you know what I mean? But I see this was a fairly late issue in the run.
The other thing I never would have expected was that cameo by old Sub-Mariner supporting character Tamara! So this must be all the way back to that improbable time when Bill Everett and Steve Gerber were collaborating on Namor...