The coast of India, 18th century

At present, India has a total of 12 major ports, 6 minor ports and sea-routes that connect the country to Yemen (at Aden), Tanzania (at Dar-es-Salaam), Seychelles, South Africa (at Cape Town), Sri Lanka (at Colombo), Malaysia (at Penang), Myanmar (at Yangon) etc. As per a stat of 2015-16, the Deendayal Port Trust at Kandla, Gujarat held the highest share in overseas trade among all while the Mumbai Port Trust had its highest share in coastal cargo trade. Going back in history, India had always been a major trade hub, majorly because of its coastline attached to three major water bodies - the Arabian Sea, the Bay of Bengal and the Indian Ocean. This makes the following countries as India's maritime neighbours at present: 

1. Bangladesh
2. Indonesia
3. Myanmar
4. Pakistan
5. Thailand
6. Sri Lanka
7. Maldives

Rounding up the clock to the colonial era, certain ports on the Indian subcontinent connected travellers and merchants all across the globe, particularly for explorers to find new sea routes to Asian territories. The Indian waters are witness to numerous naval battles that were fought between colonial powers, particularly the Portuguese, the Arabs, the Venetian and the Turks, all to strengthen their hegemony over India, and consequently, Asia. The various kingdoms and empires on the vast Indian subcontinent allowed these powers to trade with Indian ports, thus opening Indian lands to the dark age of colonization, that lasted till the 20th century. Most of the important ports and harbours of the colonial era still hold importance today. But some names are less-heard, majorly because of the rise of other metropolitan harbours. Taking reference to a 1749 dated map by Isaak Bröuckner (1686-1782), listing down the numerous ports and harbours that connected India to the outside world. 

1. Gigat (Jigat or Dwarka, Gujarat)
2. Mangalor (Mangrol)
3. Gogo (Ghogha, in Bhavnagar, Gujarat)
4. Surate (Surat)
5. Vaccos (Vaso, in Kheda, Gujarat)
6. Gandiva (Gandeva, in Navsari, Gujarat)
7. S. Jean (Sanjan, in Valsad, Gujarat)
8. Jarapor (Tarapur, in Palghar, Maharashtra)
9. Basseen (Vasai)
10. Choule (Chaul, in Raigad, Maharashtra)
11. Andavajapor (?)
12. Dabul (Dabhol, in Ratnagiri, Maharashtra)
13. Sestra (?)
14. Magapour (?)
15. Rajapour (Rajapur, in Ratnagiri, Maharashtra)
16. Corapatan (Kharepatan, in Sindhudurg, Maharashtra)
17. Tamama (?)
18. Vingorda (Vengurla, in Sindhudurg, Maharashtra)
19. Goa
20. Carwar (Karwar, Karnataka)
21. Onor (Honnavar, Karnataka)
22. Batecala (Bhatkal, in Uttara Kannada, Karnataka)
23. Barcelor (Basrur, in Udupi, Karnataka)
24. Mangalor (Mangaluru) 
25. Cananor (Kannur, Kerala)
26. Mahe
27. Calicut (Kozhikode)
28. Paniam (Panayam, in Kollam, Kerala)
29. Cranganor (Kodungallur, in Thrissur, Kerala)
30. Cochin (Kochi)
31. Tegapatam (Thengapattanam, in Kanyakumari, Tamil Nadu)
32. Tutucurin (Thoothukudi, Tamil Nadu)
33. Ramandaburam (Ramanathapuram, Tamil Nadu)
34. Cap Comorin (Kanyakumari, Tamil Nadu)
35. Negapatam (Nagapattinam, Tamil Nadu)
36. Ponticheri (Puducheri)
37. Porianovo (Parangipettai, in Cuddalore, Tamil Nadu)
38. Sadras (Sadurangapattinam, in Chengalpattu, Tamil Nadu)
39. Pondi (?)
40. Madras (Chennai)
41. San Thome or Meliapour (Mylapore, in Chennai)
42. Paliacato (Pazhaverkadu, in Thiruvallur, Tamil Nadu)
43. Poncre (Ponneri, in Thiruvallur, Tamil Nadu)
44. Senacori (?)
45. Caletor (?)
46. Nelour (Nellore)
47. Carera (?)
48. Armegon (Armagon or Durgarazpatnam)
49. Condegam (?)
50. Montepoli (Mandapalli, in East Godavari, Andhra Pradesh)
51. Petapoli (Nizamapatnam, in Guntur, Andhra Pradesh)
52. Mazulipatam (Machilipatnam)
53. Porte Gondewar (East Godavari)
54. Visigapatum (Visakhapatnam)
55. Bimilipatam (Bheemunipatnam, in Visakhapatnam)
56. Sommevaron (Somavaram, in Krishna, Andhra Pradesh)
57. Maningapata (?)
58. Pointe des Palmiers (Palmyras Point, Odisha)
59. Fause Pointe (False Point, Odisha)
60. Cicocol (Srikakulam, in Andhra Pradesh)
61. C. Carapar (?)
62. Balassor (Balasore, in Odisha)
63. Pipley (Pipli, in North 24 Parganas, West Bengal)
64. Coulpi (?)
65. Chandernagor (Chandannagar, in Hooghly, West Bengal)

These are the ports marked on the referenced map; not necessarily denoting all the ports of India back then. At the end of the 15th century, the two Portuguese navigators Pêro da Covilhã and Vasco da Gama linked sea routes between Calicut to Mombasa and Malindi (in Kenya). The former also travelled via the chief Persian Gulf ports of Iran - Hormuz and Bandar Abbas connecting it to Goa, which would soon become the capital of Portuguese India or Estado da Índia. 

The map also marks the islands of Lakshadweep, the Andaman-Nicobar group and the island nation of Maldives in pronunciations uncommon to present ears. The Lakshadweep islands are marked as a bunch of scattered islands namely Cheiro Baniam, Padoue, Chetta (Chetlat), Bearmur, Kittau (Kiltan), Corme, Mincoy (Minicoy) etc. The Maldives is shown divided into Timor, Peragua, Malique, Ketta, Candicale, Camdalu, Zamphar, Collomatis, Adoumatis, Suadou etc. Lastly, the Andaman is mentioned as Andamaon while there is no change in the spelling of Nicobar islands.