In the Hunt/YMMV


 * Nightmare Fuel: The seabed ruins boss, a giant living statue, turns out to be organic once you deplete its health. Its head explodes, revealing a bloody, flesh-like interior with eyes dangling out of their sockets...
 * Awesome Music: The Channel.
 * Demonic Spiders:
 * Bomber enemies drop a stream of bombs almost constantly. If the bombs are damaged, they just turn into flaming bombs that can still destroy your submarine.
 * The Antarctic Ocean Stage as well as the final stage has the golden sea mines. These explode into a burst of eight indestructible bombs when destroyed. They also can start a chain reaction with other sea mines, causing a lot of smaller bombs to be fired off...
 * The Deep Dark Sea stage has grey, futuristic deep-sea submarines. That fire off indestructible aimed shots. And start coming in a column of SIX. And they come at you indefinitely unless you progress further to the right... The only good thing is that they can't take much damage. Starts at 2:25 here.
 * The Sunken Town stage has a seemingly endless amount of large submarine enemies that fire homing missiles and can deploy smaller drones. Thankfully, they can be easily destroyed by attacking the drone hatch.
 * Goddamned Bots/Boats:
 * Almost all the stages have annoying little yellow robots that drop bombs on you if they are above the water, and launch homing missiles if they are underwater. They also come in great numbers, and sometimes they will just drop on you from nowhere.
 * Annoying patrol boat enemies that spawn endlessly will try to drop depth charges on you in some areas.
 * There are also endlessly spawning helicopters that do the same too.
 * Scrappy Level:
 * The Deep Dark Sea stage. At one point you have to manoeuvre through lava vents that spew out lava balls that travel in annoying arcs. At another point, you are pitted up against endless waves of high-tech submarines that fire INDESTRUCTIBLE aimed plasma shots. The first few waves only consist of two or so, but later on you have to fight against SIX of them in a column from the top to the bottom of the screen! Not to mention that the three-headed dragon-whelk was That One Boss too. Prepare to die A LOT on this level...
 * The final stage, due to the first section being chock-full of golden sea mines, and the area right before the Final Boss is the Death Course mentioned at the top of these tropes.
 * That One Attack: The Final Boss uses an attack where it generates a minefield of INDESTRUCTIBLE small red mines in two of its phases. Said attack resembles a Bullet Hell, and this attack is the only one that those two phases will use.
 * That One Boss: Two of them.
 * The first is a three-headed, fire-breathing cross between a dragon and a whelk. While its attacks are not too hard to avoid, there are lava vents around the room that periodically spew out fast-moving fireballs that can easily kill you if you're not careful.
 * The Final Boss can be counted as one too. In two of its phases, it fires out a LOT of indestructible, annoying red mines that float to the left of the screen, where you will need to worm your way through. In its final phase, it has two attacks that are relatively moderate to avoid, but the main problem is that it has A TON OF health.