Just fishing

I was out fishing on my dock one day when I thought a baby seal was swimming up from the deep. I live on a fresh water lake that runs directly into the ocean and have heard of seals and other things getting stuck in lakes like this. But as it floated to the top I relized I had never before seen anything like this. I decided to video tape it some. That's when I started to zoom in and see internal features like organs or something. Then went and got my net. I got it out of the water and it must have weighed 20-30lbs. and probably about 2 1/2 ft long. As it was sitting there on my dock I noticed it looked as if it were dissimulating or something. Almost as if it were melting. I got out my video camera again and video taped it. It was very odd. It then seemed to just melt away. I posted it to my Facebook. And no one could come up with anything. Well after weeks of searching I seen a page on ctenophores. But it had me curios because I read that they are only found in the ocean. I was hoping you guys could help tell me what it was that I found. I can send the video in an email if that is possible. Thanks