Phrasal Verbs
to go gradually into a less active, happy, or pleasant state She sank into a deep sleep. He sank deeper into depression.
to go, or to make something sharp go, deep into something solid The dog sank its teeth into my leg (= bit it). I felt her nails sink into my wrist.
to spend a lot of money on a business or an activity, for example in order to make money from it in the future We sank all our savings into the venture.