You're not going to be ocean front in Manuel Antonio. There are several hotels with beach access or within walking distance to a beach but none right on the beach. The majority of lodgings however are located along the ridge road leading to the national park, many with spectacular ocean views down the coastline.
Manuel Antonio is a small park with a good deal of wildlife, a near perfect sheltered beach cove inside the park, and a fun public beach right outside the park entrance with much bigger waves. There are lots of activities, excursions, restaurants and hotels in a small area leading to the park. Some people are unhappy with the density of tourists in this area while others are thrilled there are so many activities to enjoy and restaurants to check out. The area as a whole is very lush and green - no highrises lining the waterfront. You don't need a car to enjoy this area as it is well served by taxis and a public bus that runs from town to the beach.
Dominical, roughly an hour to the south is very different. Every bit as green and lush with plenty of wildlife, but a fraction of the tourists spread out over a much larger area. Difficult to explore without a 4WD as the roads up into the hills are very steep and unpaved. There is lots to do in this area and great accommodations at all price points but very few choices beachfront and only a slightly large number within an easy walk of the beach. This is surfing territory although there are some beaches around Uvita that are generally safe for swimming. Much better choice for adventurous travelers with their own wheels that want to get out and explore, rather than rely on organized tours.