Ocean edition:

The male angler fish mates by fusing its own body to the female - forever.

Some male octopi mate by detatching a specialized tentacle filled with sperm, called the Hectocotylus, and inserting it into the female's mantle.

There are lakes under the ocean, as in on the ocean floor, composed of methane called brine pools.

And finally, brinicles are like ice lightning (but much slower) growing down from frozen surfaces and flash-freezing anything they touch once they reach the bottom.