Traveling to Nicaragua is a great trip: it's got two great coasts, tons of adventure, gorgeous views, and it's not too crowded. One of my favorite places there is the Pacific beach town, San Juan del Sur. This place is a great place to relax at great restaurants and go beach hopping during the day. The beach directly in front of the town is not the nicest, some boats pull in and out and it's still old-school fishing town. Not a full-out marina, but there a few fishing boats are out there. Hence the suggestion to 'beach hop' around the area.
Admittedly, it can be quite lazy with the beaches and restaurants, but if you are looking for excursions they are there. There is a travel office in the center, and the town is small enough to walk around during the day. If you have means to a car, there are great resorts to check out, deserted beaches (which will probably involve off-roading in an SUV), or Costa Rica is only a 20 minute drive.