You need all 8 heart tanks for this one
Chill Penguin: (Beat Flame Mammoth first)
Use fire shot on the first igloo above the Ride Armor cave
Storm Eagle: (Needs Dash Boots)
At the start of the stage ride the contraption to the top, then dash off the top to the left you will land on the heart
Launch Octopus: (Might need Storm Tornado? Not really sure on that)
When you reach the rising whirlpool tubes you will find a battleship in the water. Sink it, to unlock a hidden room with a seadragon bot. Carefully beat this guy without falling in spikes to earn your heart.
Flame Mammoth: (Beat Chill Penguin first)
When you reach the area with the miners throwing pickaxes just slide on the frozen floor for the heart
Boomerang Kuwanger (Beat Chill Penguin, Get Arm Part)
Yea you can do this without the ice but why bother? Charge up Shotgun Ice and ride the Penguins corpse to grab the heart. Its located near the end of the stage
Sting Chameleon: (Beat Launch Octopus, Get Boots)
Near the beginning there is a pit with some breakable rocks and a large pit. You can't cross this until the stage is partially flooded, at that point you can easily dash jump to grab it
Spark Mandrill: (Dash Boots)
In one of the blackout sections after the mid boss its hiding in the upper right corner before you go down ladders protected by those weird spiked unicycle bots
Armored Armadillo: (Easier with Fire Shot)
Located at the second giant mining bot, if you blow him up before he disables the way to get the heart you can just climb the wall and grab it.