Designed to protect your noggin, thus saving brain cells and making hard objects hurt less bad, when unintended forces are applied.
WRSI-Whitewater Research and Safety Institute designed their Current for multiple energy absorbing impacts at an affordable price ($79). WRSI really excels in water sports helmet design, in that they have created a helmet that can absorb multiple high energy impacts.
Your typical whitewater helmets are not designed with much energy absorbing impact technology, let alone multiple impacts. In higher end, more expensive helmets the idea seems to be that a hard shell (often composite) outfitted with Mini Cell foam will do the trick, but in all reality the hard shell will transfer the energy directly through the foam and onto your noggin with no barriers set in place to absorb that impact.
You would be better off wearing a cheap bike helmet that is designed to crush and absorb the energy of the impact so your head won’t have to. Unfortunately this design would have likely saved your few remaining brain cells, but would be left in and unusable state.
Again, this is where WRSI really excels in their creation of a water sports helmet that will help adsorb the high energy of an impact but can still be used time and time again.