Everyone knows ... nothing attracts hot, young naked women like a badass grotto (just ask Hugh Hefner) which might be why Elin Nordegren is officially SCRAPPING plans to build one at her post-Tiger Florida mansion.

TMZ has learned ... Elin's engineer has filed documents to alter the specs on her multi-million dollar mansion re-building project in North Palm Beach.

In the docs, the engineer notes that Elin has decided to 86 the pool grotto and make a "slight reconfiguration" in the shape of the pool.

As we previously reported, Elin bought the place for a cool $12.5 mil ... then leveled it to build her dream home from the ground up. Clearly, money is not an issue.

For the record, Hugh Hefner has several mattresses surrounding his grotto ... for naps.

Naps.