A personal submarine is a submarine, usually privately funded and constructed, which is usually primarily intended for recreational use.
Some are used also for scientific purposes.
The other uses includes tourism, filming, water sporting, rescuing and spying. Some are as huge as 285 meters long in length with capacity to stay underwater for several weeks (eg. Migaloo submarine yacht). Those personal submarines which are available for sale costs from 16,000 USD to 2+ Billion USD. Wide range of them is available from 1-person to 34+ occupants, some can go just 12 meters underwater and some can even reach to Marina Trench.
Such submarines can be designed from scratch by the builder or built to available plans.
CosmicMe.com has developed a comprehensive search engine for all available personal submarines for sale with 10 different filtering options and compare facility.