submerged vs subsurface

submerged

adj

  • below the surface of a liquid 

  • underwater 

  • hidden 

  • poor, impoverished 

subsurface

adj

  • below the surface 

noun

  • A surface which is a submanifold of another surface. 

  • Something that is below the layer that is on the surface. 

How often have the words submerged and subsurface occurred in a corpus of books? (source: Google Ngram Viewer )