Typically a radshark has at least three eyes and two dorsal fins. At full size, they are generally large enough to swallow an adult sized pony whole.
Generally, the radshark is passive to creatures that do not resemble fish in any fashion. However, the scent of fish oil mixed with blood will cause a radshark to frenzy.
They are very resilient to toxins, evidenced by devouring entire schools of the highly poisonous flufferfish and suffer no ill effects.