The past tense of "sink"

What is the past tense of “sink”? Not the past participle, just the plain ole past tense.

I say “sank.”

(poll to come)

I fired a torpedo and the ship sank.

I fired a torpedo and the ship was sunk.

You sunk my battleship!

Skunk.

Sank is past tense. Sunk is the past participle (i.e. you can use it as an adjective)

Sinked

I sink
I sank
I had sunk

Submerged.

Basin.

Stainless steel sinks

Stainless steel sank yesterday

Stainless steel has always sunk

Look! Sunken stainless steel!

[Boris Karloff]
The three conjugations of the word are, and I quote: sink, sank, suuuunk!
[/Boris Karloff]

His boat sunk yesterday.

Active or passive voice? Sank and sunk, respectively.

[Thurl Ravenscroft]
The three conjugations are as follows, and I quote: sink, sank, suuunk!
[/Thurl Ravenscroft]

Karloff did the narration, Ravenscroft the song.

Passive voice uses the past participle, doesn’t it? So for the past tense it’s always “sank” for you, I guess.

The Titanic sinks/is sinking.
The Titanic sank.
The Titanic has/had sunk.

Swam vs. swum is the one that always gets me. He swam to shore? He had swum there yesterday? Is that right?