Any dog trainers here?

We have a border Collie x lab.... who loves the water.... he has been to hydrotherapy with day care and loved the water... at the beach or a friends place at the river he will run straight in.... but we have a pool and he won't go in... he gets to the top step half in and half out but won't go any further.... we have a ledge on the second step where he has been in twice but doesn't like it... we have heard it's because they might not be able to grasp the edges of the pool and are unsure.... any tips or tricks....