The biomechanical adaptations of the world are not limited to wheeled vehicles only - virtually every facet of life from stoves and heaters to entire building systems incorporate organic components in one way or another. the sea is no different - indeed, frequent severe storms along most coastlines and rough waters across the globe lend quite an advantage to the sailor whose boat can literally think for itself. the augmentations of nautical technology are varied and wide-ranging, but the basic plan of most vessels boils down to a metal chassis for a hull, shaped and meshed with the flippers, engines, propellers, organs, and external shape of the organic components.

Unlike the relatively low-space components of land-based vehicles, the increased need for both muscle mass and buoyancy means that these individuals usually have a higher ratio of organic to mechanical parts, and many have "heads" that house sensory organs instead of them being scattered throughout the body as in cars, or completely absent as in subway trains. in most waters, extreme cold conditions and emergency energy requirements also place a thick layer of fat inside the outermost hull and along the extremities of the vessel. all vessels posses markedly high levels of intelligence due to the mental demand of internal structures and aquatic navigation, as well as a magnetics-based global navigation sense similar to that found within homing pigeons. manned vessels additionally contain a control room with a direct control system like those seen in cars or busses, along with a secondary auditory organ to allow the vessel to hear both verbal commands from the captain or pilot and any sounds from the surrounding ocean.

Open water ships are capable of maintaining speed continuously for weeks or even months in transit between ports, but require herculean caloric input to do so even under optimal conditions. size class and haul weight both raise this need significantly, and most boats have large storage ports dedicated solely to storing nutrient dense dehydrated foods and vitamin capsules to be continuously fed into the internal "mouth" to retain energy. often, one or more crewmembers sole purpose aboard a ship may be to keep the ship fed and the stores maintained. closer to coastlines or along particularly well traveled sea routes, specialized ships carrying only stores of ship-feed patrol to prevent the possibility of starvation - a death sentence for craft and crew.

Certain craft retain the ability to submerge completely, sealing all entrances to internal rooms and using a modified gill organ to filter oxygen to crew within. this ability is used both as a means to hide (from either inclement weather above or enemy eyes) and as a way to scout for large aquatic game, a common goal of fishing vessels. ships that dive are usually 'wet deck' meaning that the top decks are streamlined and watertight to create minimal drag while submerged. 'dry deck' vessels have regular squared cockpits.

Seafaring biomechanical vessels are classified in a three unit system - a letter(size class), a number(cargo rating), and a name(model). the size class of a ship is self explanatory, and works in a 9-increment scale from A to J, excluding E (a specialized prefix code reserved for emergency craft). the cargo class is a percentage classification representing how much of the physical space of a vessel is dedicated to non-critical use, such as cargo or passengers. The model class is typically a short word or name - Wren, Fiddle, Jack, etc - which denotes the specific breed or build of the vessel. an example of a ship's nautical code could be B-40-TAMA, indicating a small boat with 40% space of the TAMA standard breed.

SIZE - craft from A to F are singular organisms just as biomachines on land are, but G class and above vessels exceed the limit of viable life even under oceanic conditions; the absurd size of the vessel would cause significant mobility issues and impossibly high caloric requirements in cohesive organisms, rendering them unable to function. Instead, G+ ships consist of multiple single-purpose organic components under manual or semi manual control, supported by mechanical shelling. even with this workaround, J class ships are extremely rare, the enormous manpower and onboard supply requirements causing them to be less efficient than smaller craft. a J class warship may have as many as several dozen individual simplified organisms performing different roles from propulsion to waste processing.

CARGO - the cargo rating represents generally how much of the vessel can be used freely - meaning the amount of volume within a given craft not taken up by the guts, engines, control bays, staff bunks, maintenance tunnels and storage, fuel storage, and other things essential to the minimum functioning of a ship. a pleasure craft never intended to leave the port where it was born may have a rating as high as 80 or 90, as it will never be active long enough or in strenuous enough conditions to require on-water refueling. conversely, a freight hauling vessel set to travel across large distances or dangerous seas is unlikely to rate above 50 or 60 due to the fuel and food requirements of such conditions. some scouting ships may even have ratings as low as 0, since the information gathered can be easily stored in a notebook small enough to fit under a desk. each size class has a 'maximum' rating beyond which vital systems may fail or function poorly, inducing high stress, pain, and even death in a ship (and quite possibly its crew).

MODEL - as with land craft, nautical vessels are categorized by standardized breeds, sub-breeds, or layouts, depending on the size and structure of an individual. in order for a breed to be recognized and given a name within records, it must either have a. a reviewed blueprint as well as means and intent of production at scale, or b. a stable population of breeding individuals and vessels in service. an individual ship that is not of a recognized breed may instead be registered under a layout to which it is most closely matched. although edits, natural variation, and wear-and-tear are expected within normal functioning, a sufficiently altered craft may be instructed to undergo reclassification. for example, a breed might be something like a Fennel, a domestic breed of generally smaller craft with robust swimming in adverse waters and high agility, known for a border-collie like focus on tasks and frequently favored by small scale fishermen of rough waters. a layout could be a Breeze, and entail a "narrow bellied craft of middling dive strength with low ceilings and a build inclined towards speed" most usually applied to customized or specialty bred racing craft.