Looks like the two tiddly wheels may be set high as the front one seems to be off the ground several times and he's riding on a pretty flat surface. He has two wheel steering but the little wheels look really flimsily hung to me. Like I say the front one as he heads towards the camera is wobbling like a supermarket trolley wheel (the trolley you'd take back to the rack and swap for a better one!).
He even makes a 'thing' about it being amphibious when it is obviously so unstable in the water as to be dangerous.
Hate to be so critical but he is no way ready to even consider offering the thing for sale. He should spend more time testing, ironing out the problems, accept unbiased third party criticism and I honestly think, redesign his mechanicals. He has a nice looking body which deserves to sit on a well sorted chassis and drivetrain. I really hope he has a think and gets some advice before going further.