Hello Anasauvalle,
Mochima is definitely a great dive spot. Alas all the coral in Morrocoy has died off; therefore diving in Morrocoy is not as great as it once used to be. On the other hand there are still some pristine dive spots of the coast of Mochima in the Sucre state. For some reason, in my opinion, the water is definitely colder here than in Morrocoy or Los Roques. There are some off the beaten track dive spots, which are not you're traditional dive spots thriving with local and foreign tourists. For example, there is Chichiriviche de la Costa (different from Chichiriviche close to the Morrocoy National Park) located approx. couple of hours west of the airport. You have to be expereinced as you must dive deep to see the big fish and the famous sunken christ. Alternatively, there are a few dive spots in the Henri Pittier National Park, again for experienced divers as the currents are strong. There is also one location, far off the beaten track, which is the Farallon Centinela, a rock that jutts out of the water a couple off kilometers of the coast of Higuerote in the Miranda state, about 2 hours from Caracas. This is home to some very big fish such as whale sharks and manta rays. This option is also for experienced divers.
ScubaSusie - I depends where in Los Roques you dive - but you can definitely see some big fish such as: "Mero Guasa" (Big Grouper), a variety of sharks, rays, turtles and other sea critters that will make you're Los Roques diving experience unique. Please bear in mind that some places in the Los Roques Archipelago are closed off to the public for conservation purposes.
Travel safe!
All the best,
Thomas
Caracas
berry_venezuela@hotmail.com