As already mentioned, safety plays a big role in underwater photography. But it's not just the quality of the housing that matters, their application can also be critical. Depending on the system, how a housing is closed, a mistake can happen quickly.
The greatest risk present the O-rings. These form the seal between two components of the system and are prone to leakage if mishandled. With Ikelite housings, as with the vast majority of other housings, there is one O-ring for the lens port and one for the back plate. The big advantage of Ikelite is the back plate. It is completely transparent. This allows you to always have a look at the O-ring and the inside of the case. This is a big advantage over most other systems, which usually only have a small window for the camera display. So large amounts of water could enter without being seen. With the Ikelite housing, you can see it immediately and hopefully react.
The o-ring on the lens port is unfortunately not visible on the Ikelite housing either. To my knowledge, this is not possible with any of the manufacturers.
If you want even more security, you can also install an electronic leak detector. Ikelite itself does not offer this, but the leak detector can also be easily installed by other brands.
Another safety feature is the vacuum pump. With it, practically all the air can be pumped out of the housing. If there were a leak, air could immediately re-enter and you would notice it on the pump's display.
The many knobs and levers on the case have some play, but are still tight.