Convert Appsearch query to Elasticsearch query

I am using Appsearch/Enterprise search at the frontend, but I need some heavy processing / complex queries to be made at the backend for which I need more control. And as per my understanding appsearch is basically a wrapper around the Elasticsearch so there must be some criteria based on which appsearch query translates into Elasticsearch query and then it is executed on the respective index. So I want the actual Elasticsearch query whenever I make a particular query at the frontend.
Please help me out on this as I couldn't find any such thing in the documentation.