I read through the previous messages on this topic, but they don't help that much. I have been through the moat several times, found a lever at the bottom of this tunnel underwater, but all it did was open a gate to get at the same lever. How exactly does one get into the castle? Someone earlier said there was a lever or button on the west wall of the castle moat hidden in shrubbery, but I couldn't find it. Thanx for all the previous help.

I had the same problem -- be sure to watch your automap (lower left corner). You need to get past that lever and swim around to the south side of the castle. There's a broken-down part of the wall there. The narrator even points it out to you

after ya trip that lever swim up & catch yer breath ; then ya take another lil swim & watch yer map when ya come out of the wnd grate ya will be on the other side of that wal that drops down & then as stated previously just stroll along til ya get the narration about the crumbled portion of the wall