A new study considered everything from kelp-forest barriers to seal contraception to ward off sharks along Cape Cod’s beaches but found no magic-bullet method for guaranteeing public safety.

Instead, the study, which several local towns helped launch after a deadly shark attack last year, amplified a message Cape Codders have already had to digest: The only way to completely avoid sharks is to stay on dry land. The report from Woods Hole Group Inc. found some potential utility in methods like buoys to detect tagged sharks,...