The Ocho Rios Margaritaville is part of the American chain that has colonised several Caribbean cruise ports, and it is exactly what you'd expect: loud, colourful, rum-punch-heavy, and reliably crowded when ships are in port. It has a waterslide into the sea, a swim-up bar, and a terrace over the water. The food is unremarkable.
As a place to drink in the sun with a view of the bay, it works fine. It makes no claims to authenticity or local character, and none are required of it. Families and cruise passengers find it convenient and uncomplicated. Prices are higher than the local bars in town.