When you spawn at the “Water Takeoff,” the game puts your vehicle at the height of your cockpit, not the bottom of your vehicle. This is problematic since most planes have their cockpits near the top, so the game spawns you underwater. Sometimes when you spawn underwater, your plane flips over while trying to get to the surface because of the floats at the bottom. So, it is nearly impossible to take off with most planes unless you move the cockpit down in the designer, which may make the plane not flyable. @AndrewGarrison