In the opening scene between Tiberius and Thrasyllus, it is explicitly stated that Augustus's elder grandson Gaius has died, while his younger brother Lucius seems to be in his early 20s and plays a significant part in subsequent events. Their mother Julia is just beginning her scandalous behaviour and has not been discovered by Augustus and banished. Here is the correct order of events. Julia was banished from Rome in 2 BC. Gaius was given the rank of Consul two years later in 1 AD at the age of 19. His brother Lucius died of a sudden illness the following year, 2, at the age of 18. In 3 AD Gaius was on campaign in Lycia (on the southwestern coast of modern Turkey) when he was treacherously wounded, and in early 4 he succumbed, aged 23. Neither of the brothers died in a boating accident.
We see a musician playing pan pipes, but the sound is of a recorder, not invented until the middle ages.