I came across this rare 1970 original underwater housing for Leica M4 on eBay. After 3 bids the price is at $15,200.00 and the reserve is still not met. There is not much information available online for this housing except this PDF file (in Italian). Few years ago, there was an underwater housing for Leica M8, but I have not seen any other models since.
Here is the description from the auction:
"Extremely Rare & in Mint condition, unused, Leica Elcan Navy Type KG-24A Underwater Housing. Originally built for the US Navy. Comes with original carrying case & instructions manual. In total only 50 of these were made, only a few are known to still exist!!! Manufactured by Ernst Leitz Canada Ltd Midland Ontario, in 1970. The subject is mostly an airtight container with a goal, which can enclose a Leica M4. Two side handles facilitate the grip by the use of gloves. On the "top" is: the lever charged, the switch times, and the knob of the focus but it must be done to estimate. Next to charging lever is a porthole to check the frame counter. A sight to sight, style "rear sight", allows you to frame your subject. The two gaps in relief around the outside which is housed inside the lens 90/2.8 Elcano, suggest the possibility of including a hood with snap-on. The inscriptions around the lens Elcano, are: the number of federal standard "Federal Stock Number "(WH6720-00-111-5819) and the type of model for the Marine KG-24A, serial number 240-0043 Elcan 90 f/2.8 lens.This version, painted in orange, was supplied to U.S. Navy divers."