Autonomous surface vehicles (ASVs) and autonomous underwater vehicles (AUVs) have the potential to revolutionize marine observation by expanding the scale and reach of data collection. These technologies can gather ocean data over broad temporal and spatial scales with minimal human intervention, making them a cost-effective way to scale observation systems. Autonomy promises to deliver greater manoeuvrability, longer endurance, and reduced operational risks, making it an ideal solution to the critical challenges faced by existing marine observation methods. By leveraging autonomous systems, researchers can generate new perspectives and gain a deeper understanding of the ocean. CSIRO has developed a mission planner for active perception with heterogeneous marine vehicle fleets, which can generate optimal plans for complex marine information gathering tasks in underwater environments with limited communication bandwidth. To ensure comprehensive ocean data collection, the algorithm plans efficiently over long horizons and balances exploration of the environment with exploitation of features of interest within a limited mission duration, using prior knowledge to guide the decision-making process. The presentation highlights the capabilities of CSIRO's mission planner in generating comprehensive marine observations and addresses its potential to revolutionize the field of oceanography.