Read it through once

He told me that he believed himself to have gone under the keel of the steamer, and to have been struck on the head in rising. The injury to his chest (which rendered his breathing extremely painful) he thought he had received against the side of the galley. He added that he did not pretend to say what he might or might not have done to Compeyson, but that, in the moment of his laying his hand on his cloak to identify him, that villain had staggered up and staggered back, and they had both gone overboard together, when the sudden wrenching of him (Magwitch) out of our boat, and the endeavour of his captor to keep him in it, had capsized us. He told me in a whisper that they had gone down fiercely locked in each other’s arms, and that there had been a struggle under water, and that he had disengaged himself, struck out, and swum away.