Sirena Beach isn’t all too different than some of the previous levels, as there are some Blue Coins specific to certain episodes, while the rest of the coins can be gotten on Episode 8. As usual, let’s tackle the episode-specific ones first, then move onto the general coins.
Blue Coin #1
There are three coins that require you to visit the casino, which once entered, cannot be exited. One is specific to Episode 5, while the other two are gotten from that one or Episode 4. Thus, it’s best to stick to Episode 5. When you enter the casino, there are two bunches of small slot machines on either side. Immediately upon entering, to the left set of machines and Ground Pound the top of them until you get a Blue Coin.
Blue Coin #2
While still in the casino, you will see that there are two lit torches on either side of the room. Spray the one on the right side until it goes out to get this coin.
Blue Coin #3
Immediately upon entering the casino, turn around and look at the wall above the entrance to spy some graffiti. Clean it up to get the Blue Coin.
Blue Coin #4-#7
For these, you will be entering Episode 6, where you are timed in cleaning up the beach of the sludge. Since you don’t have the option to explore and begin right with the timer, it’s best to complete the cleaning first. While doing this, you will notice four Noki residents covered with the goop. Clean them all to get the four Blue Coins.
Blue Coin #8
When you start, locate the chairs in between the two pools of water; there will be two Noki sitting on them. Right next to chose chairs will be a little plaque of sorts, so spray it for a Blue Coin.
Blue Coin #9
From the beginning of the level, head to the opposite end of the beach and look in the water by the edge of the stage for a Blue Coin.
Blue Coin #10
There are two little huts in front of the hotel, one of which has some NPCs underneath it. Head on over to the vacant one and look underneath the roof to find a Blue Coin.
Blue Coin #11
Near the previous coin, look at the wall near the small set of stairs to find some graffiti. Clean it to earn another Blue Coin.
Blue Coin #12
While facing the hotel, head to the right side of the building to find a flower bed. Spray the center of it with some water to make a Blue Coin pop out of it.
Blue Coin #13
While still in the same vicinity of the hotel, get on the upper ledge of it by doing a Side Somersault and using the Hover Nozzle. On the backside of the hotel, on the upper ledge, will be the Blue Coin.
Blue Coin #14
In front of the hotel entrance, there are four torches on either side. While facing the entrance, you will want to spray the second torch from the left, on the left side to get a Blue Coin.