The 53-65 torpedo family are Russian made, wake-homing torpedoes designed to destroy surface ships. The 53-65 became operational in 1965, while the 53-65K and 53-65M both became operational in 1969. The 53-65KE is an exported version. They are members of the Type 53 torpedos. China received an unknown number of 53-65KE torpedoes from Russia after purchasing 4 Kilo class submarines in the 1990s.
Instead of using active or passive homing as other torpedoes do, the 53-65 torpedoes use wake homing, which, upon finding the wake of a ship, turns to follow the wake to guide itself to the ship. The torpedoes have no way of telling which way the target ship is headed when they reach the wake, so they aren't as effective as other means of homing. To date, there have been no reports of a countermeasure that can confuse these torpedoes, making them very successful when they do home on to a ship.
The Royal Navy's fascination with Trimaran vessels, with trimaran hulls at one time even being proposed for its new aircraft carriers, may be in part due to the desire to reduce the wake of their ships and their vulnerability to wake homing torpedoes.