There is are ahadith that narrates about a fish called Al-Anbar (or Ambar) that a group of sahabas came across while they were on an expedition to capture a Quraish caravan by the sea shore. I related this story to my children as part of our fish theme. Below are the links that describe the incident.
We also talked about Asma-al-Husna. Allah is Ar-Rahman, The Most Merciful. Allah is Ar-Raaziq, The Sustainer. Allah provided sustenance to the sahabas in the form of a huge beached whale out of His mercy.