As a solo player sea serpents are incredibly annoying. The moment they start to lose a fight it seems they turn tail and run, which wouldn't be a problem, but the mob render distance at sea is pitifully small and they regularly disappear on me. I think it's dumb a bore or graydwarf will chase me for miles but a sea serpent becomes a big cry baby the moment an arrow hits em. Their AI should stay close to you once you agro them. Once you sail out of the ocean biome they will retreat.
Secondly their drops. As a solo player I don't have the luxury of having four people to drag a serpent onto dry land with me. Because of this I can only fight them in the water. This makes it pretty much impossible to get their scales for a shield. I think along with their meat, the scales should float as well.
Right now serpents are sorta unfair to solo players and I think these changes could help make them a viable and fun enemy to face that is worth the hunt.