WRITTEN BY CASEY BERNARD Mornings on the water in Castine Harbor are serene and picturesque. The still, glassy waters are interrupted only by the bobbing head of a harbor seal peeking from below or a gull diving for breakfast. Since the summer of 2025, residents and visitors have been able to experience these breathtaking moments under the guidance of a coxswain leading a small crew of rowers into the harbor with the newly formed nonprofit, Cast…