If experts' warnings are true, swimmers around the world can expect to experience these unwanted love taps in greater numbers than ever before.

"Jellyfish and tourism are not happy bedfellows," says Dr. Lisa-Ann Gershwin, author of the recently published book, "Stung! On Jellyfish Blooms and the Future of the Ocean."

Gershwin says popular beach resorts around the world are seeing huge increases in jellyfish "bloom" activity, a result of overfishing and changing water temperatures.

"The French and Spanish Rivieras, Chesapeake Bay, the Great Barrier Reef, Hawaii ... some of the numbers are staggering," says the American scientist who's now based in Australia.