Nautilus Tomb (オウム貝の墓場) is the second stage in Ghost Sea.
- Lord Gravey appears with a boss shockwave after 6.7 seconds200f.
- 2 Mr. Moles appear after 16.7 seconds500f.
- After 20 seconds, Zroco starts to spawn every 23.3~30 seconds700~900f.
- After 23.3 seconds700f, Znache starts to spawn every 26.7~33.3 seconds800~1000f.
- After 40 seconds, Kang Roo starts to spawn every 53.3 seconds1600f, up to 4 can be seen.
The lineup can vary drastically, but the overall strategy is the same. The idea is to lure Gravey at the start of the stage, build up a mass of cats, and kill the Mr. Moles before eventually killing Gravey. More specifically, use Ectoweight Cat to knock Gravey back, and use midranged (250-350) shockwave/long distance cats to kill the other enemies, primarily the Mr. Moles. Then, eventually, Gravey will die to your onslaught of Cats and you will win the level. The most important part of the level is to not send meatshields: a cat with range below 350 will slip behind the Mr. Mole's attack range, but only if there are no cats in front of it. A meatshield ensures that the Mr. Moles will land their hits and destroy your backline.
A sample lineup might be Biohazard + Bony Bones, Ectoweight Cat (37), Manic Macho Legs (30), Castaway Cat (35), Golfer Cat (30), Housewife Cat (30), Cyborg Cat (50+11), and the default Cat Cannon. Other cats that are useful include Masked Yulala, Pizza Cat with a shockwave talent, Cat Base Jr., Express Cat (for sniping the Kang Roo), and Weedwacker Cat. For the above lineup, you need to spam all the midranged attackers except for Cyborg Cat. There still needs to be Cyborg Cats to take out the peons and Kang Roos, but you need to prioritize your LD and Ectoweight Cats to keep the Mr. Moles and Gravey at bay, respectively. With a Rich Cat power-up, this concern is mostly alleviated. It is a no-brainer to use the default Cat Cannon as it syncs up the Mr. Moles.
Alternatively, Li'l Valkyrie Dark (30) will knock back a Mr. Mole in 2 hits of her shockwave, and has a perfect range of 340 with a high movement speed to boot. She breaks the stage and can even be used with meatshields and still win.
The title might refer to Jules Verne's novel Twenty Thousand Leagues Under the Sea. The novel primarily explores the adventures of Captain Nemo and his futuristic submarine, the Nautilus from the perspective of some Englishmen. At the end of the novel, a dying Nemo asks his crew to leave the submarine via a boat and to flood the submarine, burying it and Nemo himself under the sea. In Nemo's own words, "To-morrow I will be dead, and I wish for no other tomb than the Nautilus."