Ferry was from Talaimannar to Rameshwaran Island and part of rail link from Colombo to Madras (I think). There was a small ferry for each vehicle from Rameshwaran Island to Mainland India.
22 miles, the same distance from Dover to Calais. Couple of guys have swum it too. One such was Kumar Anandan, swimming from Sri Lanka to India and back in 51 hours, in 1971. While attempting to swim the English Channel on 6 August 1984 he collapsed and died due to heavy currents. Other trivia; Kumar Anandan hailed from Valvettithurai, the village of the Thalaivar, i.e. Prabhakaran.
Almost all Tea Estate indentured workers were brought by Ferry and had to walk thru thick jungle to Tea estates in the hill country. Quite a few died, no records were kept.
The Brits did not give the Estate indentured labor Ceylon Citizenship. Because that would mean they would be under Ceylon Labor Laws which were quite reasonable. Would defeat the whole purpose of getting slaves in all but name.
It became an issue after independence. The estate Tamils were almost 15% of the population. Half were repatriated back to India, with even Ceylon Tamils voting for the move.