Things That go Bump in the Night

I rarely sleep through the night when we are on the boat.  Every few hours I wake up and check to make sure the boat hasn't filled with water, or washed up on the shore, or started on fire, etc.  Most nights I wake up on my own, check things to make sure everything is OK, and go back to sleep.  Some nights something happens to wake me, the most common event is that the wind picks up and makes enough noise to disturb me.  The past few nights the things that are waking me have taken a turn to the bizarre.  Our first night in this new anchorage both Nicole and I woke up at the same time, but we couldn't identify what woke us.  As I got up to do my normal checks I saw that our GPS position hadn't changed since we anchored, but the depth sounder showed only about half the depth of water under the boat that I expected.  I turned on the other sounder we have and it agreed that we were quickly running out of water.  With nothing to do short of pulling the anchor in the middle of the night and trying to re-anchor, I set my mental alarm clock to wake me in an hour and went back to bed.  An hour later, the depth was still dropping, and according to our tide charts we would run out of water well before low tide.  None of this made sense, we had checked the depths when we anchored and had more than enough water, and we hadn't moved since then so there shouldn't have been any change.  I continued to monitor the situation, low tide should have occurred about dawn so there would be some light to see what was happening.  When I checked the depth next, it was just starting to get light outside, and everything was back to normal and we had plenty of water under the boat.  The next night we stayed in the same place again, and shortly after we went to bed we were both awakened again, this time from something hitting the hull of the boat.  I got up and went out on deck to check, but didn't see anything on the boat or in the water around us.  When I got back into bed, we heard a fish jump just outside the boat, and then another, and then something hit the anchor chain.  This happened several more times through the night, and confirmed what I had suspected the night before.  The bay we were in was full of pink salmon, coming to spawn in the stream at the head of the bay.  During the day we had seen large schools all over the bay, numbering in the thousands, and at night they had been drawn to our boat by the anchor light.  There were so many that it was causing the depth sounder to read them and not the bottom of the bay.  The second night we had seen seals and a sea lion close to the boat just before dark, and that was the noises we were hearing, the panicking salmon trying to escape the seals and running into the boat or the anchor chain.  The other option is a giant squid sleeping under our boat, and every once in a while reaching out and shaking the anchor chain.  I didn't see any tentacle prints on the hull the next morning, so I'm sticking with the salmon story.