Allowed? Based on what angle? If it's protecting fools (in your opinion) from themselves, it raises the question of liberty vs. safety; does the government own you, or should you as a free-willed adult of informed decisional capacity be master of your own choices?
On the other hand, if you are concerned people putting themselves in harm's way might teach great whites people are defenseless and edible (albeit not an optimal choice), leading to someone elsewhere getting attacked, that's another story, and the question becomes what is our best reasoned speculation on the risk (I cannot imagine we have scientific studies on it!)?
I'm not 'cheering for Darwin' to 'get' people doing things I consider dangerous, anymore than I take that attitude when people try to climb Everest, ski dangerous slopes, etc... Nor am I interested in tackling one to stop him, or calling police to intervene. Some problems in this world are not mine (or ours) to solve.
Richard.