Maybe if you went in with him and kept him on a long line. (?) You could test him out and see if he's afraid or not. He might like the feel of the water on his skin and might like to swim around a little... but maybe just needs a little extra security of your touch and being right there close with him. You could even hold a bumper or stick out in front of him that he could smell and have something for him to focus on so he might not care as much about seeing where he's going...and let him get hold of it off and on. That's too bad that he's blind. But they are pretty adaptable, aren't they.