Neptunian transportation
For Neptunian-kind, motion is a thing that everyone always does. Sometimes you need more than your own webbing, though!
Living an ocean-world, Neptunians naturally have a talent for swimming, with the stamina and speed to get them to most places they need to go. That said, there are occasions where self-power might be insufficient, such as navigating the streets of a dome-city. Thankfully, Neptunian technology is accommodating to those needs.
In general, movement devices are personal-scale, for one or two riders. A large reason for this comes from their tradition of individuality and personal style: A jetbike is as much an accessory an extension of who they are as it is a tool. Almost always, they're designed by their rider. That isn't to say that there are bog-standard ones, they are just far from common: the most frequent example being an off-worlder using a rental.
Psi-bonding
The other reason for this is the Neptunian's affinity for psionic connections. Typically, when one fabricates vehicle fabricated, they go to a local technician, that fits it with an AI. The vehicle's intelligence is set to communicate exclusively to it's creator's wavelength, and as the rider uses its craft, that AI learns and develops its own personality to match, essentially becoming a partner to the rider. Someone who isn't bound to a vehicle can still pilot it, but except in rare circumstances, doing such is considered a pretty harsh faux pas (and, expectedly, said craft won't function as well).
This psi-bonding can be performed on animals, the most common example being the Pelagic Corps of the Lifeguardians with their characteristic riding mantas. In those cases, there is a implicit degree of consent between the rider and the mount: the psi-bonding comes out of a degree of trust and friendship between the two. As such, bonded mounts are incredibly loyal and affectionate to their riders.
It is also said that, on rare circumstances, a living creature's intelligence can be extracted, and transferred to a craft to serve as a living intelligence- supposedly even more capable of handling a machine than an AI...But you'd be hard-pressed to get any details from a native.
Spacecraft
Due to the Neptunian propensity for mindblindness, it is somewhat uncommon for them to want to go visit other worlds. That said, it's also a bit of a challenge for other ships to land on Halcyon or Neptune due to lack of actual land- so the more sociable few run trade and transit vessels throughout the system.
Spacecraft are designed much in the same way as aquatic craft are, just much rarer: Going into space is usually a thing reserved for the thrill-seekers and the extreme explorers. That said, even a smaller frigate is expectedly much larger than an on-world craft, and as such, the AIs they design are insufficient to fully control all systems. In most cases, when a spacecraft is finished production, either a friend or a volunteer will have his consciousness transferred to the ship, to serve as a living navigator, either for as short as a trip to the moon Triton or on a permanent basis. This has twofold advantage: Not only can they help maintain the ship and plot appropriate courses, they can serve as a companion for the pilot, and help stave off the loneliness of communication with mind-blind individuals.
While most on-world vehicles resemble fish or common marine life, celestial vehicles often look to the uncommon. Tentacles are a common feature, tending to mimic squid or jellyfish; often times they look as if they may be bearing growths of kelp or lichen along their sides.
Neptunians don’t really believe in armies, or any sort of military spacecraft. That’s silly. Why would they want to fight anyone? Maybe, like, a rad sound-and-light system...
