Layered coastal defense for strategic peninsulas

What is a sensible naval defense strategy for peninsular states bordering important seaways?

Build layered sea denial with SSKs, mines, and small missile craft, adapting the same principle to the technology of earlier periods.

A modern Spain- or Italy-like state could combine diesel-electric submarines, minefields, and small surface missile craft. Each layer complicates an opponent's movement through confined waters and forces it to divide attention among underwater, mine, and surface threats. Earlier eras would use the same logic with period-appropriate weapons.