The ocean is full of some incredibly odd creatures. It feels like the further you go down, the stranger and more alien-like ...

The Birch Aquarium’s 18-foot-long (5.5-meter-long) tank has three leafy sea dragons — two males and one female — and 11 weedy sea dragons. The 5,300-gallon (20,062-liter) tank is a vast space, ...

It also is trying to breed leafy sea dragons. The Birch Aquarium's 18-foot-long (5.5-meter-long) tank has three leafy sea dragons — two males and one female — and 11 weedy sea dragons.

It also is trying to breed leafy sea dragons. The Birch Aquarium’s 18-foot-long (5.5-meter-long) tank has three leafy sea dragons — two males and one female — and 11 weedy sea dragons.

It also is trying to breed leafy sea dragons. The Birch Aquarium's 18-foot-long (5.5-meter-long) tank has three leafy sea dragons — two males and one female — and 11 weedy sea dragons.

It also is trying to breed leafy sea dragons. The Birch Aquarium’s 18-foot-long (5.5-meter-long) tank has three leafy sea dragons — two males and one female — and 11 weedy sea dragons.

And then, “out of the blue,” Brodt said, “it happened.” Last May, aquarium staff members discovered that a male weedy sea dragon was successfully carrying his mate’s eggs.

The 5,300-gallon tank is a vast space, especially for the smaller leafy sea dragon, which grows to only about 14 inches in length. The tank has grassy plants, a sandy bottom and rocks.

When sea dragons mate, they engage in a kind of “courtship dance,” in which the male and female slowly spiral upward together. SeaWorld’s sea dragons kept reaching the surface too quickly.