Shipping transit time?

Ordered a koi online. Seller shipped 2nd day air because cost was too much for them for next day air. I opposed this idea and was willing to pay more than the shipping they quoted on the listing. The seller shipped anyway for 2nd day air. According to them they receive koi second day and have had delays receiving 3 days later with no issues. I’ve had bad experiences not receiving fish next day. Other sellers have shipped next day and I have not had a problem. I also have not seen anywhere ship koi second day. What are the chances the koi survives? Thoughts?