A sea trout is just basically a brown trout which has migrated to sea. They can be caught during the day, especially if the water is carrying a bit of colour. They tend to be very wary and if you are fishing for them during the day in low clear water, you need to use small flies, fine leaders and a lot of stealth in approaching the water. The cover of darkness just gives the angler the advantage of being able to approach them more easily and they tend to move into shallower water then and are more responsive to the fly.
