Pair of metal objects that reflect sound much more to the direction where the sound came from, could be identified from their mutual distance and bearing. Their bearing and distance to the ship sonar gives ship location.

This works with simpler and weaker sonar than the kind that is needed for shipwreck searches.

Traffic signs have retro-reflectors for light. Some moonlanding sites and satellites have them with narrower beams. Radar reflectors are used and incidentally this for sound would probably also happen to work for radar too when the object is above water but that does not matter.

The object might be 5 meters wide, stainless steel and coated with teflon. It is just dropped to sea and it sinks upright. Later it's exact position is measured and put to database.

If it is really needed, a drone boat might stay near it, constantly pinging with sonar and transmitting navigation signals with radio to passing ships and planes.

Many men buy expensive sports cars partly because they hope the cars will attract women. What if sports cars could take this idea a step further by actively helping their owners get dates?

Imagine a woman walking by a parked Ferrari and stopping to admire it. The car notices her interest and starts a conversation. It introduces itself, tells her a little about its owner, and asks whether she'd like to know more about him.

If she's interested, the car could show her photos and videos of its owner on a display visible from outside the car. She could also ask the car questions about him.

The car could even ask whether she'd like to exchange contact information with its owner. With her permission, it could take photos or videos of her, perhaps recording a short personal introduction to send him.

The whole interaction could happen while the owner is shopping, eating at a restaurant, or doing something else entirely.

Naturally, the car would need to respect privacy and consent. People should be able to decline or end conversations easily, and photos, videos, and contact information would only be collected with permission.

Sports cars have traditionally been passive status symbols that might help attract romantic interest. This would turn them into active matchmakers, capable of introducing their owners to potential dates even when the owners aren't around.

What do you think of this idea?

Some book covers have textures that certain people find extremely unpleasant to touch. I once encountered a book like this myself.

What if schools and businesses were required to use paper with similarly unpleasant textures to encourage people to communicate electronically instead?

The idea wouldn't be to make paper dangerous or cause actual skin irritation, but to make it uncomfortable enough that people would naturally prefer digital alternatives.

Unlike banning paper, this would keep it available when needed while creating a built-in incentive to avoid using it.

Of course, different people have different tactile sensitivities, so finding a texture that most people dislike without causing harm could be challenging.

Essentially, instead of making digital communication more appealing, we'd make paper communication less appealing.