The seas in BKB are exactly the same as in vanilla, and the next trun I checked to see wether they did indeed have any ships along North Africa, but they only had one of Algeria.
Some new updates:
I can't launch a Crusade against Constantinople, because the Byzantines are allies of the Pope. I have no allies, even those who are not allied with my enemies do not want to ally themsleves with me. Then unexpectidly, without even being excommunicated, the Pope sent its troops to attack me in Naples! I managed to beat them off (I thought for a moment wether even resisting His Holiness would get excommed), but decided not to invade the Papal States and Rome as the last thing I need now are a bunch of angry, devout peasants revolting in Brittany and Anjou. Fortunately, I have managed to build a fleet of caravels (only saving them by sending them into the Central Med, where the Byzantine ships can't get me) and pretty much destroyed the Med fleet of the Byzantine Navy. The Danes, on the other hand, still blockade my Channel ports.