Check out this site. I was on a little trip to Hopkins, Placencia and Punta Gorda a couple of weeks ago and found this place. I didn't stay there, but looked at the cabanas and property, right on the water, and very well maintained. http://www.lost-reef.com/
THey have a restaurant and bar right on the property also.
A note, be patient when emailing them because they dont have internet service on site, they have to go into Placencia for their email. The resort is located before you get to the Placencia penninsula.