One of the most active seaports in Spain is Cadiz in the South, not far from Gibralter. Cadiz was originally a Phoenician colony, one of the oldest Western Europe going back to nearly 1100 BC. The ancient Phoenicians were also known as Canaanites, and they occupied the lands that today are known as Lebanon and Northern Israel, an area that was fairly heavily forested at the time with Pine trees that were essential in the construction of boats (it's no accident that the center of maritime culture in the Levant region ran from Canaan in the south up to southern Turkey in the north, given the presence of such trees there). Jewish traders would often then take Phoenician ships to their respective trading colones, including Cadiz, and would frequently form Jewish ghettos there as a consequence.
The Romans were at best indifferent maritime traders - their strength was in their army, and while they used ships (think the invasion of England by Julius Ceasar), their ships tended to sink because they had comparatively few good shipwrights or the raw material for ships. The Italians never really managed to develop into a colonial superpower for precisely that same reason, and it has always seemed a bit odd to me that Columbus would have had the knowledge and connections to become a sea captain. However, if he's family was in fact from the area around Cadiz, then it is far more likely that he would have learned his trade and gained the relevant connections through his Spanish Judaic relations.
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