After a mighty storm has passed, You discover a old waterlogged chest, sealed with chains and weighted with stones. You find drowned form of a young animal. Suddenly, the creature's eyes open you have acquired an unusual pet.
Martial training: In adolescence you trained with the weapons of your people and learnt how to use them proficiently (work with your DM to determine details)
When you become an adult you learn to used a weapon (of your choice) appropriate for your culture and social standing. (work with your DM to determine details)