Shipping Dry Ice by Ocean in 2026: IMDG 42-24, UN 1845, and the Cruise-Port Twist

When shippers think about dry ice in logistics, they usually picture an air shipment — a small parcel, well-insulated, racing to a hospital or a lab. But ocean freight is increasingly part of the dry-ice conversation in 2026, and the regulatory environment changed materially on January 1, 2026, when IMDG Code Amendment 42-24 became mandatory. Pharma cold-chain shippers, food exporters, and even the cruise-port logistics ecosystem in South Florida are all affected.

Here is what changed, what stayed the same, and how to ship dry ice by ocean without giving up days of sailing time to a hold.

What IMDG Amendment 42-24 actually is

The International Maritime Dangerous Goods (IMDG) Code is updated on a two-year cycle. Amendment 42-24 was published in 2024, became permissible for voluntary use on January 1, 2025, and became mandatory on January 1, 2026. Any shipper still referencing the previous Amendment 41-22 on Section 14 of a Safety Data Sheet or on shipping declarations is now non-compliant — and carriers are catching it at booking.

The 42-24 amendment runs to roughly 300 individual changes. The ones that matter most for dry ice and cold-chain ocean shippers in 2026:

• New UN numbers for sodium-ion batteries (UN 3551 / UN 3552) and for hybrid and sodium-ion vehicles (UN 3556 / 3557 / 3558). Generic UN 3171 “battery-powered vehicle” can no longer be used for lithium-ion or sodium-ion vehicles after January 1, 2026.
• New entries for fire-suppressant devices (UN 3559) — relevant for shipments to vessel operators and offshore.
• Carbon black and charcoal are no longer broadly exempt and now require classification review.
• Recycled plastics material definition expanded to include IBCs.
• New “degree of filling” definition affecting packaging selection.
• Updates to placarding for battery-containing containers; Maersk now recommends four-sided placards on Special Provision 962 containers.

Dry ice in ocean freight — the rules that govern it

Dry ice ships as UN 1845, Carbon Dioxide, Solid (Dry Ice), Class 9. The key ocean handling requirements:

1. Venting packaging is mandatory. Dry ice sublimates from solid to gas, and any sealed package becomes a pressure vessel as it warms. Outer packaging that prevents pressure relief — sealed steel drums, jerricans, sealed plastic bags as outer — is prohibited.
2. Container ventilation is required. A standard reefer with dry ice loaded inside must have ventilation that prevents CO2 accumulation to dangerous levels. CO2 displaces oxygen and creates asphyxiation risk for anyone opening the container.
3. Documentation must reflect the dry-ice quantity. Not just “Class 9, miscellaneous” — actual net weight of dry ice on the dangerous goods declaration.
4. Stowage and segregation rules apply, including separation from heat sources and from incompatible cargo.
5. Crew warnings — vessel personnel must be informed of the dry ice presence so they don’t open the container without ventilation.

Why ocean dry-ice volume is growing in 2026

The pharmaceutical cold-chain market hit $22.75 billion globally in 2025 and is on track for $44.1 billion by 2033 — a 9.12% compound growth rate. Air is the historical default for the very temperature-sensitive end of pharma (vaccines, biologics, cell and gene therapies), but ocean reefer is 7-10 times cheaper than air on a per-kilogram basis, and the industry is actively migrating bulk biologics and longer-life products to ocean wherever lane economics and shelf life allow.

That migration is driving more sophisticated use of dry ice in the ocean lane — not as the primary cooling medium for a multi-week voyage, but as a supplementary medium at the front and back ends of the journey, or as redundancy for refrigeration failure. South Florida is a natural beneficiary: PortMiami and Port Everglades both handle high volumes of pharmaceuticals into Latin America, where the inverse flow — pharma from the U.S. into Brazil, Colombia, Chile — is growing rapidly.

The cruise-port twist nobody talks about

Port Everglades and PortMiami are also two of the largest cruise ports in the world. Cruise ship provisioning — pharmacy stocks, specialty food, samples — involves regular dry-ice movements between dockside warehouses and vessels. These movements are subject to IMDG too. Cruise operators have tightened acceptance procedures in 2026, and provisioners who used to wave dry-ice paperwork through casual port-side handovers are now being asked for full dangerous goods declarations and audit trails.

What can go wrong — and how to keep it from happening

• Sealed outer packaging. A well-intentioned operator adds an outer plastic bag for “extra protection” and creates a non-compliant package. Solution: explicit packaging diagram in the SOP; no field substitutions.
• Underestimated sublimation. Dry ice sublimates at roughly 5-10 pounds per 24 hours per insulated container in tropical ocean conditions. A 7-day voyage with insufficient dry ice arrives warm. Solution: model sublimation against realistic ambient temperatures.
• Documentation tied to old IMDG amendment. Shipper’s declaration references 41-22; booking is refused. Solution: document templates reviewed and updated against 42-24 quarterly.
• Crew asphyxiation incidents. Rare but devastating when they happen. Solution: clear container labeling, written notice to vessel master, and PPE/ventilation procedures at all opening events.
• Reefer failure with dry-ice backup not engaged. The pallet was prepped with dry ice as backup, but the procedure for activating it was unclear. Solution: explicit decision protocol with the carrier and on-vessel crew.

Practical playbook for shipping dry ice by ocean in 2026

1. Audit your shipper’s declaration template against IMDG 42-24. Every Section 14 SDS, every dangerous goods declaration. If anything still says 41-22, it’s wrong.
2. Match dry-ice quantity to actual voyage time + buffer. Build in 25-30% over the calculated sublimation, not 10%.
3. Use venting outer packaging. Approved fiberboard or vented metal — never a sealed outer.
4. Notify the carrier and vessel master in writing. Verbal handovers are not sufficient in 2026; carrier dangerous goods desks expect formal notification.
5. Train the receiver. Asphyxiation risk at delivery is real. The receiving warehouse should know to ventilate before opening.
6. Pair with a carrier that knows the lane. Maersk, CMA CGM, MSC, ZIM, and Hapag-Lloyd all have current dangerous goods desks comfortable with UN 1845. Smaller NVOCCs vary.

Go-Freight’s dry-ice and cold-chain capability

Go-Freight ships dry ice by air and ocean out of South Florida — from short-cycle parcels to full cold-chain pharma movements through PortMiami, Port Everglades, and MIA. Our dangerous goods desk works to current IMDG 42-24 and IATA DGR 67th Edition standards, prepares all declarations and packaging, and coordinates carrier acceptance ahead of booking. Contact us to get your dry-ice and cold-chain ocean lanes properly built against the 2026 rules.