In order to start the Waterpop Arena Event Lost Ark Gold, you'll need to head over to the Maharaka Promotion Manager located in any main city. After accepting the light pink [Event] quest you will be tasked with traveling to the island called Mahaka Paradise. Maharaja Paradise is located to the west of Wavestrand Port, in East Luterra. You can search for any location on the Map at the top right text box.
Once you've arrived at the island you can complete the quests for a small reward of 10 Maharaka Leaf and 1000 silver. There is another quest that can be repeated once daily per roster for 100 Maharaka Leaf. Take note that only characters that have traveled to the island will be able to use the Ocean Liner to get back. It would be wise to either leave a character there or set a Bifrost location to save time traveling back in order to make it in time for the event.
The Water Pop Arena is located on a platform near the center of the island. The portal will appear every 2 hours on even hours (12 am, 2 am, 4 am, 6 am, 8 am, 10 am, 12 pm, 2 pm, 4 pm, 6 pm, 8 pm, and 10 pm). These times are the server's time and the exact time will depend on which region your server is located. You can enter the event multiple times per day.
The amount of Maharaka Leaf you receive for each event completion varies depending on your performance and if your team wins or loses. If you come in 1st place on your team for points and your team also wins you will receive the maximum reward at 250 Maharaka Leaf. The cheapest Lost Ark Gold very minimum you can earn is 50 Maharaka Leaf if you perform poorly and your team also loses.