What is International Sea Freight, and How Does It Work?

International sea freight connects different countries and continents through maritime shipping routes. It plays an important role in global trade, enabling the movement of various products, from raw materials to finished goods, between nations.

What is International Sea Freight?

Sea freight, also known as ocean freight, is the transportation of cargo and goods by sea vessels across oceans and seas. It involves the use of specialised ships designed to carry different types of cargo:

  • Container ships: Transport containerised cargo and goods packed into standardised steel containers.
  • Bulk carriers: Used for transporting loose, unpackaged bulk cargo like grains, coal, ores, and cement.
  • Tankers: Designed to carry liquid bulk cargo like crude oil, petroleum products, and chemicals.
  • Roll-on/roll-off (Ro-Ro) ships: These vessels can accommodate wheeled cargo, like vehicles and heavy equipment, that can be driven on and off the boat.

How does Sea Freight Work?

  1. Booking and Documentation: The shipper or freight forwarder books space on a vessel with a shipping line or carrier and prepares the necessary documentation. 
  2. Inland Transportation: The cargo is transported from the shipper’s premises to the port of origin, often by truck or rail.
  3. Port Operations: At the port, specialised equipment, like cranes and forklifts, loads the cargo onto the vessel. 
  4. Ocean Voyage: The vessel sets sail and transports the cargo across the ocean to the destination port.
  5. Port of Arrival: Upon arrival at the destination port, the cargo is unloaded from the vessel and prepared for customs clearance.
  6. Customs Clearance: The necessary documentation is submitted to customs authorities, and the cargo is inspected and cleared for import.
  7. Inland Transportation: Finally, the cargo is transported from the destination port to the consignee’s premises, typically by truck or rail.

Various parties, including shipping lines, port authorities, customs brokers, and inland transportation providers, may handle the cargo throughout the process. Effective coordination and communication among these parties are essential for the smooth and timely delivery of the goods.

How much does sea freight cost?

The cost of sea freight can vary significantly depending on several factors:

  • Distance: The longer the distance between the origin and destination ports, the higher the cost. Shipping routes across oceans and continents generally cost more than shorter regional routes.
  • Cargo Type and Volume: The type of cargo being shipped and the volume or weight of the shipment will determine the cost. Containerised cargo is typically charged based on the container size (e.g., 20-foot or 40-foot containers) and whether they are a full container load (FCL) or a less than container load (LCL), while bulk shipping is charged by weight or volume.
  • Mode of Transportation: The mode of transportation used for inland transportation to and from the ports can affect the overall cost. Trucking is generally more expensive than rail transportation for longer distances.
  • Fuel Costs: Fluctuations in fuel prices can directly impact the cost of sea freight, as fuel is a significant expense for shipping lines.
  • Supply and Demand: The availability of vessels and the demand for shipping services can influence pricing. During peak seasons or periods of high demand, rates may increase due to limited capacity.
  • Additional Services: Any additional services required, including refrigerated containers, special handling, or expedited shipping, can add to the overall cost.

At SLG Logistics, we can provide a personalised quote for your sea freight today to help you understand your shipping costs. 

What are the advantages and disadvantages of sea freight?

Cost-effective: Sea freight is the most economical option for large shipments, especially long-distance transportation. The ability to transport massive volumes of goods in a single voyage means lower per-unit costs. 

Large Capacity: Ships can carry an enormous amount of cargo, making sea freight ideal for bulk shipments and large quantities of goods. A single container ship can transport thousands of containers. 

Versatility: Sea freight can accommodate a wide variety of cargo types. 

Environmental Impact: Despite the large volumes, sea freight has a lower carbon footprint per ton-mile than air or road transport, making it a more environmentally friendly option for long-distance shipping. 

Global Reach: Sea freight connects ports worldwide, allowing businesses to access markets across different continents and regions that may be challenging to reach by other modes of transport.

Safety: Modern shipping practices and technologies have made sea freight a relatively safe mode of transportation, with advanced tracking systems and secure containerisation reducing the risk of loss or damage.
Reliability: While sea freight is slower than air freight, it has predictable schedules and transit times, allowing for better planning and inventory management.
Slower Transit Times: Sea freight is significantly slower compared to air freight. Ocean voyages can take several weeks, making it unsuitable for time-sensitive shipments or perishable goods.

Weather Dependency: Sea freight is subject to weather conditions, which can cause delays or route changes. Severe storms or adverse weather can impact schedules and potentially damage cargo.

Limited Accessibility: Sea freight is restricted to coastal areas and major shipping ports. Inland destinations require additional transportation methods like land trucking, which can increase costs and transit times.

Complex Documentation: International sea freight often involves more complex paperwork and customs procedures than other shipping methods, which can be time-consuming and challenging.

Potential for Delays: Port congestion, customs inspections, or equipment breakdowns can lead to unexpected delays in the shipping process.

Less Flexibility: Once the cargo is loaded onto a vessel, it’s challenging to make changes or retrieve items mid-journey, unlike air or road freight, which offers more flexibility.

Risk of Damage or Loss: While generally safe, cargo damage can still occur due to rough seas, improper stowage, or container accidents. 

How long does sea freight take?

The time sea freight shipments take can change depending on several factors:


The primary factor affecting transit time is the distance between the origin and destination ports. For example:

  • Transatlantic routes (e.g., Europe to North America): 1-2 weeks
  • Transpacific routes (e.g., Asia to North America): 2-4 weeks
  • Europe to Asia: 3-5 weeks
  • Europe to Australia/New Zealand: 4-6 weeks

Port Efficiency

The efficiency of loading and unloading operations at origin and destination ports can impact overall transit times. Some ports are known for quick turnarounds, while others may experience usual congestion.

Vessel Speed

Modern container ships typically travel at speeds of 16-22 knots (18-25 mph). However, some shipping lines practise “slow steaming” to reduce fuel consumption, which can extend transport times.

Route and Stops

Direct routes are faster, but many shipments involve multiple stops at intermediate ports for loading and unloading, which adds to the overall transit time.

Customs Clearance

Depending on the efficiency of local customs procedures, the time required for customs clearance at the destination port can add several days to the total shipping time.

Inland Transportation

Additional time should be factored in for inland transportation from the shipper’s location to the origin port and from the destination port to the final delivery point. 

Choose Sea Freight with SLG Logistics 

When it comes to sea freight shipping, SLG Logistics is your trusted partner for all your international shipment needs. If you’re looking to export from the UK to ASEAN countries or ship goods across other global routes, our expert team is here to ensure a smooth and efficient process.

Don’t let the complexities of sea freight shipping overwhelm you. Let SLG Logistics take care of your transportation needs, allowing you to focus on growing your business. Whether you’re new to international shipping or looking to optimise your current logistics processes, we’re here to help.

Contact us today to discuss your sea freight requirements. Our team of experts is ready to provide you with personalised solutions and guide you through every step of the shipping process. With SLG Logistics, you have complete peace of mind that your cargo is in safe hands.

Contact us today to learn about our international freight forwarding services from the UK to Southeast Asia.

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