With a tip of the hat to wolfgang...
Lake Champlain has long been surrounded by rumors of a mysterious creature akin to the Loch Ness Monster. The locals call him "Champ," and he is officially a protected species in both Vermont and New York State.
And after so many decades of stories and speculation, Champ has been spotted!! Scientists, eager to learn as much as possible about the potentially prehistoric lake monster before he disappears again, have quickly assembled all of the maritime and scientific equipment that they might possibly need. However, owing to Champ's thoroughly protected status, officials have mandated that no experiment shall be conducted which might pose an immediate risk to Champ's life or health; in particular, they stipulate that Champ can not be removed from the lake at any time, even momentarily (nor can the ecosystem of the lake be impacted such as by draining the lake).
Can you find a method to determine Champ's inherent buoyancy?
Can you find a method to determine how much Champ would weigh if he were allowed to be hoisted out of the water and placed on a scale?