What is the fine-grained topic of the following text: This SC-30 tourist submarines have the capacity to transport up to 28 passengers (and 2 crew) or 42 persons to a diving location, dive to a depth of up to 30 meters, explore the undersea world, surface, and return to port - all that under its own diesel or electric power. Only return the topic.
Features and capacities of SC-30 tourist submarines