Originally posted by Nyu:

their are fixed sea serpent spawns and random. if you find one midday remember that spot (mark it) they will respawns every few days again near that.
atleast thats how it was before mistland.
night and storm they just have alot higher spawnrates to appear randomly

Serpents never has fixed spawn points
Only global spawns of 5% at night ( + 5% if rain or storm ) each 64mx64m fields

Originally posted by cookie:

there are still daytime spawns , the only change ive seen is the chase rate - they used to give up after one minute of chasing you if they didnt hit you , now they seem to give up after about 30 seconds , which makes it harder to lead them to shore - you need them near shallow water to get the scales
i dont hunt them specifically - i go on trips to find mushrooms and collect the serpents on the way there and back , the most ive seen in a row was 3 -
expert tip - frost arrows

Serpents dont have "Normal" daytime spawns , only if raining or storming in daytime ,that serpent will stay there until you hunt her , maybe can be confused by a daytime spawn but surely was spawned when you passed in that zone when rain

And night time spawns will despawn in daytime :(