(CNN) — Here's one bit of good news for the environment -- and your 2019 travel wish list.
According to marine officials, thousands of new golden jellyfish have appeared in the lake.
"Ongoing monitoring conducted by the Coral Reef Research Foundation (CRRF) indicated that the jellyfish populations were now rebounding after the declines that were a result of the drought conditions experienced throughout Palau in 2016," said a government statement issued by Palau's Koror State announcing the lake's reopening.
The lake was once home to 10 million to 20 million nonstinging golden jellyfish, hitting 30 million at its peak in 2005.
The number stabilized to around five million from 2007 until there were scarcely any medusa seen during the drought crisis in 2016.
Gerda Ucharm, research biologist with the CRRF, says there are now around 630,000 golden jellyfish, according to the last survey taken in December 2018.
While the number is still far lower than during the lake's prime years, the scientist is optimistic.
"Based on the number from December 2018, the population has not fully recovered yet; however, with this good windy and rainy weather, we should expect to see changes in the population and decrease in the water temperature," Ucharm told CNN Travel.
"If the weather conditions continue to be normal, then we are optimistic that the number should keep going up."
Jellyfish Lake, which is 400 meters long and 30 meters deep, is part of the Koror State Rock Island Southern Lagoon, a UNESCO World Heritage Site in this Micronesian nation in the western Pacific Ocean.
The harmless translucent jellies of the lake are called Mastigias papua etpisoni and are a unique subspecies only found in this particular body of water.
Experts blamed El Nino for causing the shrinking of the jellyfish population from 2006, as the rise in water temperature led to a decrease in algae growth, a major food source for jellyfish.
The number of golden jellyfish dwindled when the lake was hit by El Nino in 1998, too.
Human activities -- such as bringing non-native and invasive species and harmful sunscreen pollutants to the lake -- are also blamed for its decline.
Even a tiny pebble or piece of debris "could have a tiny living organism that could potentially become invasive in the lake," says Ucharm.
As a result, visitors are asked to brush off all sand from their shoes and empty their pockets before entering the lake area.
A communal effort
This image of Jelly Fish Lake was takien in November 2018 by the Coral Reef Research Foundation.
Coral Reef Research Foundation
Palau has a history of standing tough when it comes to environmental protection -- every visitor entering Palau has to sign an eco-pledge -- but the closing of the lake was a communal effort. "The elders wanted the lake closed to allow it time to recover," says Chris Lubba, a representative of Palau Dive Adventures, a sustainable tour agency in Palau. "Technically, the government never officially closed it."
"Many responsible tour companies stopped doing tours there and frankly there were so few jellyfish there it really made no sense to go there."
The return of the jellyfish had a positive effect on tourism almost immediately, he says.
"Our reservations are up compared to January last year," says Lubba.
"If we keep on this pace for new bookings, we'll have our best January ever. There were lots of people who canceled or postponed trips to Palau to allow for the lake to recover and now that they have heard it is open again, they are booking trips."
Palau Dive Adventures has already begun hosting tours to the lake since its reopening.
There are other marine lakes with harmless jellyfish in Palau, but Jellyfish Lake is the only one open to tourists. Others are strictly closed for conservation reasons, and only scientists are allowed to enter.
Visitors hoping to swim with the harmless medusa at Jellyfish Lake have to be accompanied by a certified tour guide and are asked to paddle gently, as the jellies are very fragile.
Also, scuba divers will have to leave their gear back at the resort.
Between 13 and 15 meters from the lake surface, there is a layer of bacteria that seals the poisonous dissolved hydrogen sulfide gas in the bottom water layer and prevents it from mixing with the top layer.
Scuba diving, therefore, is not allowed and any item accidentally dropped in the lake is considered lost forever.