As per MARPOL Annex II, describe the categories of substances and the conditions for discharge outside special areas?

flowchart TD
    A[MARPOL Annex II] --> B[Categories]
    B --> B1[Category X\nmajor hazard\nno sea discharge]
    B --> B2[Category Y\nhazard\nlimited discharge]
    B --> B3[Category Z\nminor hazard\nless stringent]
    B --> B4[Other Substances\nno harm\nno Annex reqs]
    A --> C[Discharge outside special areas]
    C --> C1[En route ≥7 kn / ≥4 kn]
    C --> C2[Below waterline\n≤ designed rate]
    C --> C3[>12 nm from land]
    C --> C4[≥25 m depth]
    C --> C5[Per P&A Manual]

• Categories: X (major hazard, prohibited), Y (hazard, strict limits), Z (minor hazard, less stringent), OS (no harm, no requirements)
• Discharge conditions (outside special areas): en route ≥7 knots (self-propelled) or ≥4 knots (non-self-propelled), below waterline, >12 nm from land, ≥25 m depth, per P&A Manual
• Category X extra: prewash mandatory, discharge to reception facility until ≤0.1% by weight, no sea discharge
• Category Y/Z: efficient stripping, Y stricter limits than Z
• Governing instrument: MARPOL Annex II, Regulation 6 (categorization), Regulation 13 (discharge standards)