Apparently, sea travel was considered taboo in many Hindu sects, if you believe "A History of Sea Power" by William Oliver Stevens. I found that hard to believe at first, and thought it was a misconception based on the author's early 20th century bias (think the kind of book that uses "Oriental despotism" seriously), so I looked around a bit and found out it was a real belief. A serious enough offense to possibly lose one's varna (i.e. caste), in fact.
What would Indian history be like if Kala Pani did not exist? Would India have been a major sea power? Am I overstating Kala Pani's importance, since many Indians found ways around it (Islam, repentance rituals within Hinduism, etc.)?