Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

Why do submarines have rounded hulls? What are some advantages/disadvantages of having a rounded hull compared to a flat one?

 Submarines have rounded hulls for several reasons. One of the main reasons is to reduce drag and increase the submarine's speed and efficiency. A round hull is more hydrodynamic, meaning it moves more easily through the water. This allows the submarine to move faster and use less energy, which is important for a vessel that must be able to operate quietly and stealthily.

Another reason for the rounded hull is to reduce noise. A flat hull can create more noise as it moves through the water, which could be detected by sonar. A round hull is less likely to create noise, making it harder to detect.

One disadvantage of a rounded hull is that it provides less surface area for the submarine's sensors and other equipment. This can be a problem if the submarine needs to carry a large number of sensors or other equipment.

Overall, the advantages of a rounded hull, such as reduced drag and noise, make it a good choice for a submarine. While there are some disadvantages, such as less surface area for sensors and equipment, these can be compensated for with careful design and engineering.