Lake Khaiyr monster

The Soviet scientist was up early that morning and was enjoying the scene of idyllic tranquillity at isolated lake Khaiyr in Yanski area of Yakutsk. Looking around Mr. Gladkika was suddenly and frightfully aware of a huge jet-black animal with a long neck and small head feeding on the grass around the lake. Scared out of his wits, Gladkika ran like the blazes to alert the head of the expedition to find mineral deposits.
When they returned armed with rifles the monster had already retreated back to the water and all that reminded to be seen was its impression in the grass. However, Gladkika found welcome relief from possible ridicule when several days later the expedition chief and two of his lieutenants saw the animal as it rose in the centre of the lake. Just like Gladkika they noticed the same anomaly that distinguishes the Lake Khaiyr creature from most other lake monsters - it possessed a dorsal fin.
Being scientists, and needing some sort of explanation for what it was that they had seen, the Russians posited that it was the last of the long-extinct species of aquatic reptile the icthyosaur. Unfortunately from their own description of the animal it is readily apparent that they are confusing an icthyosaur with a plesiosaur. The Lake Khaiyr remains unidentified to this day and because of its isolated location is not frequently visited so further sightings have been dismally few.