The Ocean Hunter

A Light Gun Game released in arcades by Sega in 1998. Set in an Ocean Punk world where human civilization is being ravaged by terrifying sea monsters, you ply the seven seas with your trusty spear-gun seeking the bounties on these beasts' heads. While the oceans are swarming with all kinds of aquatic horrors, it is the Seven Great Monsters who are your greatest prize - and your deadliest challenge.

Tragically, the game was never ported to a home console, and is now extremely rare. (Except in Singapore, where it's in practically every arcade. Go figure.)

Tropes used in The Ocean Hunter include:

Achilles' Heel: Apart from the soft-spots, each boss has a vital point that must be hit three times in order to win, including Kraken and Karkinos' eyes, Leviathan's throat and Charybdis' light.
All Myths Are True / Fantasy Kitchen Sink: All bosses and minibosses are named after mythological creatures from all over the globe.
Alluring Anglerfish: Charybdis, the nightmarish giant Angler.
Attack Its Weak Point: Every boss battle has "sweet spots" that you have to aim for.
Bait and Switch Boss: Midgardsorm.
Big Bad: The sea-god Rahab, who apparently created all of the other monsters.
Boss Rush: The final stage, Panthalassa, has you fight four sub-bosses with no Mooks in between them, then sends you up against the final boss, who has three forms.
Breath Weapon: In his intermediate form as Poseidon, the final boss spits... giant bubbles... at you.
Dual Boss: The three moray eels collectively called Hydra, the three Kerberos sharks, and the twin ribbon fish Vritra and Kaliya.
Eldritch Abomination: Rahab's final form.
Everything's Squishier with Cephalopods: Giant octopi Kraken and Umi-Bozu; giant squid Scylla. All use Combat Tentacles.
Everything's Even Worse with Sharks: You fight no less than five giant sharks: White Death, the trio known as Kerberos, and the nightmare-inducing Leviathan. Normal-sized sharks are also common enemies in the first, second, and seventh levels.
Final Boss: Rahab.
Flunky Boss:
- Leviathan is followed by smaller sharks.
- Charybdis keeps deep sea eels in her mouth for boss fights.
- Medusa and her jellyfish.
- Midgardsorm's parasites.
Gaia's Avenger: Rahab was pissed at humans for polluting, abusing, and otherwise messing with the ocean, so he created the other Great Monsters to put us in our place. Except Midgardsorm. Middy has been terrorizing the seas before Rahab made it cool.
Giant Enemy Crab: Karkinos is a textbook example. Attack Its Eyes For Massive Damage!
Go for the Eye: Kraken's, Karkinos', as well as Rahab's weak point.
He Was Right There All Along: Kraken, the giant octopus, stalks you throughout a sunken ship.
- You fight a miniboss, Basilosaurus, in the middle of a suspicious hole in the seafloor. Sure enough, when it seems you've won, the resident of that hole decides to stick its neck out and eat you and Basilosaurus. Cue the second half of the level.
Just Eat Him: Near the end of her battle, Charybdis decides to attempt this, simply inhaling you rather than spew gulper eels or charge to bite. Midgardsorm does this too, but with much more success.
Kraken and Leviathan: Pretty much to be expected in a game that focuses on destroying huge sea monsters. Kraken is a giant octopus and the first boss, while Leviathan is a Megalodon and the second boss.
Light Gun Game
Lightning Bruiser: Rahab.
Ludicrous Gibs: The natural result of shooting Midgardsorm's heart until it explodes.
Made of Plasticine: Who would've thought that a regular shark (those at the start of the game) would take less damage than say, a stingray?
Marathon Boss: Rahab.
Mini Boss: Every level except Texcoco Great Lake has at least one. The final stage has four.
Mook Chivalry: The Mini Bosses "Hydra", which are three giant moray eels. They're not very bright as they attack the protagonists one at a time, instead of all three at once. Subverted by "Cerberus", three big nasty sharks who attack the protagonists all at one go.
Nintendo Hard: This game eats your quarters like Karkinos eats whales.
Ocean Punk
One-Winged Angel: The Final Boss goes through three forms: Dagon, Poseidon, and Rahab.
Prongs of Poseidon: The Final Boss uses this in his second form. Then again, that form is named "Poseidon".
Rail Shooter
Reptiles Are Abhorrent: Mook monsters include sea snakes and prehistoric mosasaurs. There's also the sub-bosses Sea Dragon and Black Dragon (giant marine iguanas) and the boss Ahuizotl (elasmosaurus). (Despite its name, the sub-boss Basilosaurus is actually a prehistoric whale.)
Sand Worm: Midgardsorm is a textbook example, albeit one that lives in the seafloor rather than the desert.
Sea Monster: Just about every popular sea monster gets a shoutout in this game. Sharks of assorted types, sea lizards, sea snakes, octopi, eels, giant squid, oarfish, angler fish, elasmosauruses, jellyfish, crabs, prehistoric whales, marine worms, and a mad sea god. And that's just the minibosses and bosses. Many mooks are also present.
Sequential Boss: Rahab; see One-Winged Angel.
Steampunk: You travel between stages in a pimped out hot air balloon and fight with an automatic spear gun.
Strong Flesh, Weak Steel: The organic bosses can take countless shots from your harpoon gun before going down.
Turns Red: All the boss fights will have two parts: part one, fight back the boss. Part two: the boss try his last trick on you, and you have to shoot his weak point thrice. The mechanics depends on the boss (eg: Kraken will wrap his tentacles around you, Charybdis will suck you inside his mouth and so on).
Under the Sea: Have you been paying attention?
- Except for the fourth stage, which takes place in a freshwater lake (and on the bank, when fighting the boss).
Underwater Boss Battle: ...um... yeah.
- Again, except for the second half of the fourth boss battle. You get up onto some rocks and essentially play whack-a-mole, but with water instead of dirt, a harpoon gun instead of a hammer, and an irate dino instead of moles.
Underwater Ruins: Ubiquitous, but especially in Texcoco Great Lake and Panthalassa.
Warmup Boss: The first sub-boss is the easily-defeated White Death.
- Timed Mission: However, White Death is attacking a scientist, and if you want to fight Sea Dragon, you'd better be really damn fast. If the scientist dies, you don't get bonus health and... well...
Womb Level: The second half of the West Ocean takes place inside Midgardsorm, a giant worm that's swallowed you (and countless ships) whole. You're swarmed by creepy parasites and kill it by attacking its heart.