The yellow markings evoke scars that sharks accumulate as they age. They may also be a reference to tiger sharks, since Sharpedo seems to be based on several sharks, including the sawtooth shark with its mega. They may be a bit excessive, but that's hardly a reason to call the entire design shit.

It's seriously overreacting to claim one minor detail ruins a design, or that it would be perfect without it, otherwise it's shit.