Blue Coin #17 and #18
Return to the top of the left cliff and then look off to the right to spot a large alcove, hover over to it and then spray the top left and top right blocks to find the two Coins.
Blue Coin #19
Drop down to the platforms below and from the lowest one, jump and hover over to the left to land in another alcove. Jump up and to the left of the entrance here and use your Hover Nozzle to create another opening where Coin #19 can be found.
Blue Coin #20
From the previous coin, look over to the cliff on the left and then jump and hover over to this alcove to snag Coin #20.
Blue Coin #21
Yet again, hover back over to the long alcove on the left cliff and once you land, jump up and hover to reveal Coin #21 behind the wall.
Blue Coin #22
You’re getting the hang of this by now, hover back to the nearest alcove on the right with the square switches and spray the one to the right to reveal Coin #22.
Blue Coin #23
Drop down to the alcove below and spray the switch to move the wall back once again and then Wall Kick all the way up to the top right hidden passage, following it through to the end to pocket Coin #23.
Blue Coin #24
Drop down to the sea once more, refill your water and then activate the switch and climb up the right side of this cliff. Leap on to the platform on the right here and at the end you’ll find some graffiti, spray it to reveal Coin #24.
Blue Coin #25
Shoot the switch on the nearby wall and Wall Kick up the left side where you’ll spot the Blue Coin above you. Hover over to the platform on the right and then back over to this small alcove to collect Coin #25.
Blue Coin #26
Make your way to the climbing ropes now and once you reach the top of the purple shell (where you access the secret course in this Episode), jump and hover over to the alcove to find Coin #26.
Blue Coin #27
In Episode 4 or 8, head to the waterfall and dive in to reach the sea floor area of Noki Bay. As soon as you gain control here, look to the left and you’ll find the first Blue Coin here.
Blue Coin #28
From the previous Coin, keep going along this left wall and you’ll spot another Coin at the far end.
Blue Coin #29
While staying on the outer wall, look to the left and follow it all the way along to the right to come across yet another pillar with a Blue Coin on it.
Blue Coin #30
Finally, for the last Blue Coin in Noki Bay, continue to follow this left wall along to another pillar which holds the final Blue Coin, congratulations!