Yup, the early buckshot loads were indeed poor performers as the soft lead pellets flattened into disks, but with the Federal OOO Buck loads that have been introduced you have some serious performance as the pellets are hard and, even though they are unbuffered shot, flatten very little and stay together.
Here is my test that I did with the Federal buckshot load. 24" of water penetration.
Water penetration test: Federal Premium .410 000 Buckshot 4 pellet in a Bond Arms Derringer
Remember this is in a derringer, in a revolver you will get more velocity and more performance.