I have had my left ACL done twice now... I know to get back into just straight line work took 3-6 months.. although to get back into twisting and external pressure was closer to 12 months.. I can't see the actual diving being too much of a problem... but getting to the water over uneven ground could pose a problem.
Good luck with the op... things have also come a long way since my last op.. so these times may have been reduced significantly...