Tips for Training Your Dog to Use a Ladder:
It's important to train your dog when they are hot so they are more inclined to want to be in the water. Start by rewarding him with treats when they go near the ladder. Have him wear a life jacket so he is buoyant and not scared and is in a calm mode.
As he masters one step at a time, constantly positively reward him with a big reward for going up and down the steps. It will take time but you wouldn't think twice about swimming lessons for your kids!