in for an inch, in for a mile

listen to the pronunciation of in for an inch, in for a mile
Английский Язык - Английский Язык
Given that one is partly involved in or committed to a project, action, position, etc., there is no reason to refrain from becoming fully involved or fully committed

I soon found the water lapping at my toes so I figured, “in for an inch, in for a mile” and continued on in after the oystercatcher.