Monsters of the deep
It is extremely likely many"lake monster"sightings are in fact large sturgeon.Reaching lengths of 14 ft and weighing up to 1400 lbs would give them that reputation.
There are seven species in North American waters:the Atlantic,White,Green,Lake,Shortnose,Shovelnose and Pallid.
We will deal with  the two most likely candidates,the Lake and White Sturgeon.
white sturgeon white sturgeon
another giant white sturgeon,caught in the 1980's in Washington state
1500 lb white sturgeon caught on a setline in the Snake river,Idaho.It was estimated to be 150 yrs old.
another jumper
one of these landed on a fisherman crushing him....
another jumper...In 1894 Mississippi river commercial fisherman reported catching 249,000 lbs of lake sturgeon.By 1931,due to overfishing and loss of spawning habitat,the catch had declined to almost nothing..
Lake sturgeon are excellent jumpers,and even surface feed!A sighting such as this would possibly inpire comparisons to long necked prehistoric creatures.....
pallid sturgeon
the Pallid sturgeon.Of the 7 Species in North America,5 are threatened or endangered.