Burial At Sea

"We therefore commit his body to the deep, to be turned into corruption, looking for the resurrection of the body (when the Sea shall give up her dead), and the life of the world to come, through our Lord Jesus Christ; who at his coming shall change our vile body, that it may be like his glorious body, according to the mighty working whereby he is able to subdue all things to himself."

—Traditional Anglican Burial at Sea Service

A burial at sea is a form of funeral where the body of the deceased is disposed of at sea. May involve burning the ashes and then scattering them to the wind, or just dumping a weighted coffin off the side of a boat. Often an exception to It Always Rains At Funerals, though you may get some high waves anyway.

These were very common in Real Life back when sea voyages were long. If it's two weeks before the next port, you do not want to lug the body around. They still occur on occasion but nowadays its most commonly a last request in the will of an old sailor.

In science fiction, the equivalent to burial at sea... In Space! has its own trope, Burial in Space. A Viking Funeral is a subtrope with an Incendiary Exponent.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Burial At Sea include:

Anime & Manga

In the Pokémon anime, Ash & co. tried to do this with Team Rocket when they found them floating on the sea after escaping from a sunken ship. It turned out they were just unconscious, and Pikachu was disappointed.
In Hokuto no Ken 2, Captain Akashachi's body is put on a boat, which is then put to drift in the sea.

Film

At the end of Master And Commander: The Far Side Of The World, all of the recently killed crew are given a funeral at sea.
In You Only Live Twice, Commander James Bond is buried at sea.
Although not actually at sea,in Batman Returns a bunch of penguins push The Penguin's body into the river.
In The Enemy Below, 'Heinie' Schwaffer dies of his injuries, and is buried at sea in the final act of the film.
In The Godfather, Luca Brasi was buried at sea after being killed in a restaurant. This was confirmed when Sonny was told, "Luca Brasi sleeps with the fishes."
- Most likely he was dumped either the Hudson or East River.
Happens in Flight of the Intruder after one of the protagonists is killed during the first mission of the film.
In The Crow: City of Angels, Ashe Corven was dumped into the local harbor following his murder by Judah and his gang. As this is a Crow movie, he got better.
Frankie (Lenny's deceased older brother) from Shark Tale is actually given this type of funeral after being crushed to death by a falling anchor (which prompts Oscar to think that he killed Frankie, and not the anchor), where his body is tossed overboard the deck of the shipwrecked RMS Titanic (the sharks' lair) and floats to the surface belly-up.
This is how the military often disposes the dead bodies of several fallen Transformers, both Autobot and Decepticon alike in the live-action Transformers films.

Literature

Shield Sheafson in Beowulf.
Mrs. Moore in A Passage to India.
In an Alastair Reynolds story, an epic Stern Chase is underway between two vessels that routinely approach the speed of light. The second in command of the pursuing vessel is dying, and requests that her body be fired forward the next time the ship is at top speed. She jokes, grimly, that it's an old pirate custom; Burial at Cee. She even points out that the joke only makes sense in a language that hasn't been spoken in Millennia. It's still an incredibly touching moment.
In Robert E. Howard's "Queen of the Black Coast", Conan the Barbarian pushes the boat out to sea before lighting it as a pyre.

Live Action TV

In The Sopranos, after Tony Soprano and his gang kill Salvatore "Big Pussy" Bonpensiero (who they believe has betrayed them), they wrap up his body and, with heavy hearts, give it a decent burial at sea.
In The X-Files, Scully's father, a Navy captain, is cremated and buried this way while Bobby Darin's "Somewhere Beyond the Sea" (his and Maggie's wedding song) plays in the background. Scully is upset, saying that her father was entitled to a full burial at Arlington, while her mother replies that he would have wanted it this way.

Video Games

In Final Fantasy VII, Aeris is buried in a lake.
In Final Fantasy X, Yuna performs a sending on a beach.

Web Original

In Survival of the Fittest, Rick Holeman and Jim Middleton throw several bodies into the sea from a cliff as a means of giving the dead students a 'funeral'.