A verb which can be either transitive or intransitive is called an ergative verb. English has many ergative verbs.
Examples are: sink, ring, boil, speak, explode, collapse, dissolve etc.
• The explosion sank the ship. (transitive)
• The ship sank rapidly. (intransitive)
• The driver stopped the train. (transitive)
• The train stopped suddenly. (intransitive)
• Ring the bell. (transitive)
• The bell rang loudly. (intransitive)
• The sun melted the ice. (transitive)
• The ice melted. (intransitive)