Reason being I left 1 sub between more subs of mine and his axis navy task force thinking he could only push through with other naval units meaning I could submerge but if he moved in with a destroyer I thought he'd have to stand and fight the first sub or at least stop there with the destroyer if he chose not to fight thus meaning my subs behind was protected - clearly not?

Here's a screen grab - his Japanese navy with a destroyer that's now to the left of South America passed the 1 British super sub to attack several subs (USA & British) I had in the square that his Jap navy units now occupy:

Apologies for asking all these questions but I only learn the rules by making errors like this then posing the question.

So in brief am I correct in thinking destroyers in actual fact can pass over subs in an immediately adjacent sea zone (without engaging) to then fight enemy navy in a second sea-zone?