Besides swimming in this clear lagoon you can also practice other water sports. Several restaurants at the rim of the lagoon have kayaks available, and you can also dive here. Laguna de Apoyo provides a great place for eco-tourism as well. You can hike through the forest and observe lots of birds and monkeys. The view from atop is absolutely fantastic.
As mentioned before, there are several restaurants and hotels at the rim of the lagoon. They for sure provide a great spot to understand the meaning of 'tropical paradise'. Sun bathing with a cocktail in your hand, some music on the background and the lagoon on your side… what more can you ask for?
Getting to: Apoyo Lagoon
Laguna de Apoyo is less than an hour from Managua. You should take the highway to Masaya (Carretera Masaya), and pass Masaya. At kilometer 37.5 you take a right (there are some signs, but do pay attention!). Keep following the road, and take a right where it stops and hits another road (this is after about 15 minutes from the highway). After maybe one minute you can enter the road that descends to the lagoon on your left.
There are also buses that go to the lagoon, but not all of them go down all the way. Sometimes you'll have to walk the last path. Public transportation can be taken either in the Masaya Market or at the entrance of the lagoon, located in the Km 37.5.