I was wondering when or if Aeria was going to do the summer event this year due to how early the game still is, but they put it up and it's actually amazing for the items you can get from the event, the daily and repeatables there are a nice little bit of fun and the island it self is very nice on the eyes.
How to get inside
So there is 4 quests that you will pick up from any of the event NPCs that are located near any of the city/town teleportal NPCs, 2 of the quests are to kill 3 of the "World bosses" which will be shown on the world map for you, and the other is to kill 300 mobs at any location in the game, either in the open world or whilst just doing dungeons will count towards the quest, once you've done both of these then you will receive your quest reward which is a swimsuit and an accessory item both in a box suitable for your class, you will also need to take off your weapon when you want to go into the event island through the NPC.
Activities and rewards
There's plenty of different little activities to do inside from dailys and repeatable quests, some will have you collecting objects from the ground, catching fish's with nets, cooking some food, launching water balloons at moving targets or even throwing them at players in another area that opens up for 30 minutes at a time. The daily quest in the other area that's open for 30 minutes at a time gives you a "Manta reef coin" instead of the fragments that the rest of the quests give you, the coins are something you want to make sure you do each day as they're used to get harder to craft items or even an inventory pet exclusive to the summer event.
There is even the best food and Digestants which will be incredibly handy to stock up on for when you plan to do raids, as crafting end-game foods requires fragments from dungeon dailys and the Digestants are cash shop/magic lamp related items that can also be bought in the marketplace, doing this will save you a nice amount of money as it's incredibly easy to get the coin fragments from repeatables.
The main repeatable that you would want to do here is the balloon targets as you get between 1-2 fragments for something that takes barely 30 seconds or less depending on how many people are currently there as well, hitting the red and blue targets 5 times will reward you with 1 coin each where-as hitting the rainbow target which moves the quickest and is the smallest "AoE" on the balloon will reward you with 2, I farmed this for perhaps a few hours and made up to about 400+ fragments, so just with that and looking at how much each item costs on the npc, you can see just how viable this event is and taking the opportunity to do it as much as you can will save you a lot of time and effort, especially for the Primal essence to get your support equipment or to purchase Appraisers Ink.
I don't think there's any specific level cap to getting inside either so you won't need to wait till 60 to do it, if you are under-leveled then all you need to do is simply run to the zones and unlock the teleport camps as you pass by so you can very easily get back to the locations and kill the world bosses in the area, since there is a ton of people around there killing them, they basically die within 10 seconds or less so all you need to do is make sure you hit the boss atleast once to get the count for the kill.
I highly suggest doing as much of this event as one possibly could, I think it's quite rare to get events like this on games where there's multiple rewards and that most/all of them are actually very useful to obtain