Before anyone can celebrate, the man in the crows nest yells, "Captain! Something in the water!" As everyone continues to look in the direction of the speck presumed to be your destination, it appears that a set of red fins sticking out of the water is coming towards the boat. The fins fold, merging with the water, and disappear. The air is tense as the crew hopes it was just some exotic sharks. The tension is broken by the boat shaking and most of the heroes who are not used to boats likely falling down or at least dropping to one knee. After quickly getting back up, the captain yells, "It must be the dragon! Everyone, to your stations! Crew, we are no match for the beast. I will man the helm. Everyone else, focus on your own safety, and help keep the ship afloat! Heroes, do what you can to take care of the beast! It is bound to come up soon. I pray it doesn't just destroy the bottom of the boat."
If you have a magic item that gives you advantage on initiative, roll another initiative check as part of your post and if it is higher I will replace it. Otherwise I will use what I rolled for you.