Complex sentence: During the first half of the 18th century, Hydra built the same kind of vessels as were built in the other Aegean Islands: the "sachtouri" of 15 to 20 tons, and the "latinadiko" of 40 to 50 tons.
Split into simpler sentences: During the first half of the 18th century, Hydra built the same kind of vessels as were built in the other Aegean Islands. These were the "sachtouri" of 15 to 20 tons, and the "latinadiko" of 40 to 50 tons.