Every level of training has a prescribed maximum depth limit. It is worth noting that these limits are based on the assumption of perfect or near-perfect dive conditions. For example, a graduate from an Open Water 20 course is limited to 20 meters/66 feet, and all course training dives are limited to 18 meters/60 feet. Therefore, all your planning needs to be within that depth. This will limit the number of dive sites that are available to you, but that limit is reasonable because there are many potentially excellent dives within 20 meters/66 feet of the surface.