Configuration

The BlueROV2 needs no configuration: every slot the parts declare fills itself with its default. The vehicle config (bluerov2_description/config/bluerov2.yaml, or any file passed as config_file:=) states differences only.

Variants

The vehicle comes in two variants. The standard BlueROV2 carries six thrusters: four vectored horizontals and two verticals. The Heavy carries eight: the same horizontals plus four corner verticals, which add roll and pitch authority and more lift for payload. The variant is picked by the base part:

base: {type: bluerov2_chassis, name: base_link}        # standard
base: {type: bluerov2_heavy_chassis, name: base_link}  # heavy

With the heavy hull, widen the buoyancy footprint to "0.457 0.575".

Buoyancy

A real vehicle is trimmed with foam and ballast to float slightly positive, so a dead vehicle surfaces on its own. The config declares that trim directly instead of asking you to tune volumes:

net_buoyancy: kilograms of lift beyond neutral (positive floats up). The shipped default is 0.0, so the vehicle holds whatever depth it is spawned at; set it a little positive (0.002 is about right) to model a real trim that surfaces a dead vehicle.
cob_offset and cob_frame: where the center of buoyancy sits, relative to the assembly’s center of mass (com) or to base_link; keeping it above the center of mass is what makes the vehicle passively stable in roll and pitch.
fluid_density and footprint: the water and the horizontal size of the displaced volume.

The Gazebo composition realizes the declaration as a dedicated displacement volume solved from the assembled mass, so the declared trim holds when the config changes (Buoyancy).

Payload

Everything else is payload: sensors and actuators fitted into slots, one config entry each. The fitted options and their topics live in Sensors and Actuators; the slots are:

Slot	Accepts	Default
`thruster_1` .. `thruster_6` (`_8` heavy)	the matching T200 propeller	fitted
`camera`	`explorehd_camera`, `marinesitu_c3`	`explorehd_camera`
`sonar`	`ping360`	empty
`dvl`	`dvl_a50`	empty
`gripper`	`newton_gripper`, `sediment_sampler`	empty
`payload`	`payload_skid`	empty
`rack`	`roof_rack`	empty

Slot entries, free placements, ad hoc slots and topic overrides follow the same schema as the BlueBoat (Configuration keys); the instance key is of:, not on:. Mistakes fail the build or the launch with a message naming the problem.