The MPK-WE marine pack (about $135-$200, Compare Prices) works with W series Cyber-shot models, while the MPK-THH and MPK-THGB marine packs (about $155-$230, Compare Prices) work with T series models. The marine packs offer waterproof protection up to 132 feet.
In addition, Sony has introduced sports packs that allow underwater photography up to about 10 feet in depth. The SPK-WB sports pack (Compare Prices) works with the Cyber-shot DSC-W290, while the APK-WB (pictured here, Compare Prices) and the APK-THAB work with certain W and T series Cyber-shot models. The sports packs cost between $60 and $100.
Just make sure the Cyber-shot model of camera you own matches the underwater housing you want to buy.
Photo courtesy Sony