Although one quarter of the world’s seaborne oil trade passes through the region, there are few constrictions in the major shipping routes and laden tankers are mostly in transit, sailing
well offshore. However, passing ships come close to land off Cape Comorin (India) and Dondra Head (Sri Lanka), where the existence of traffic separation schemes testify to the risk of collisions.

The coastal influence is strongest off the eastern coast of Sri Lanka where currents are often confused and may flow at 3-4 knots. Occasional groundings are reported from this area. Coral reefs are widely distributed in the region and represent a significant hazard to
shipping, but reef groundings have been comparatively rare in the past. A summary of the major tanker spills occurring in the South Asian Seas region is given in the following table.

The location of shipping routes vary according to monsoon seasons and changing currents. During the south-west monsoon (May to September), the preferred route for vessels in transit passes between the Laccadive Islands and Maldives, whilst at other times ships tend to pass north of the Laccadives. In the Bay of Bengal the main seasonal weather hazard is represented by cyclones (May to November). General shipping traffic to and from the region is dominated by the trade routes linking Karachi, Mumbai and Colombo with East African and South African ports. Whilst there are 18 major ports and about 30 ports of intermediate size within the region, only one of the countries, India, is a large importer or exporter of oil.