HONG KONG'S external trade by sea totalled $1,040 billion in 1993, an increase of 8.7 per cent over 1992, according to figures released by the Census and Statistics Department yesterday. Trade by sea accounted for 51 per cent of the territory's external trade, with trade by land at 26 per cent and air at 18 per cent. The remaining five per cent was by other means including river, postal services, and goods accompanying passengers. External trade over land grew 17 per cent to $557 billion. Trade by air increased by 17 per cent to $390 billion. United States remained the biggest market for Hong Kong's exports, with 32 per cent by value going to the US last year. Exports by sea to the US grew by 11 per cent in the same period, and exports by sea to China surged 40 per cent. Re-exports led the growth in exports by ocean and land. Ocean trade was fuelled by the re-export of footwear, which grew 34 per cent to $11.23 billion. Japan was the largest supplier of the territory's imports by sea. Seaborne imports from Taiwan rose 5.4 per cent; those from the US increased 6.8 per cent. Large increases were also recorded in the value of imports of vehicles by sea, up 52 per cent to $15.89 billion.