Debris is advected by the surface current and spread by wave-driven random motion. In the ship frame each item moves with u_rel = u - v_ship plus a cross-track random walk of strength K (wave dispersion acts sideways, so each item crosses the gate once). The intake gate is a line of width W across the bow, so the expected collection rate is the flux through it:

Q = rho * W * max(0, v_ship - u_x) items per second, rho in items per square metre. Only the current component along the heading counts; the crossflow moves items sideways but does not change the flux through a uniform field.

Collected items go to five sorting lanes. Lane output is m_out = yield * m_in (plastic 0.82, metal 0.94, glass 0.90, hazmat 1.00, organic 0.60); the rest is rejected. Machine speed scales as 1 + 0.32 * level and is multiplied by a power efficiency min(1, P_supply / P_demand). Belt throughput is limited to (3.0 + 0.9*level)/1.7*0.9 items per second.

Simplifications: uniform current, no ship-wave interaction, mean item masses chosen for this page (plastic 0.35 kg, metal 0.25, glass 0.5, hazmat 12, organic 1.0), prices per kg as in the 3D game. Educational model, not a design of a real vessel.