My recent experience in the ocean has been perplexing to me. My first petrel has a push fit beckson in the front bulkhead. It kept blowing out in the surf line. well i am at times being forced out of the cockpit against my will. darn the front fills up as well as the cockpit.at this point the kayak weighs a lot and this is no hand pump job. the plate does have a small hole in it but i think it is popping out when paddling out .

The small 'breather hole' in the hatch (or bulkhead) is enough to compensate for temperature changes (usually) and to prevent disasters when hauling the kayak over mountain passes on the highway, but if the hull flexes, it could easily pop out a snap-fit inspection hatch.

If I think I'm going to 'play' in rougher water with an unloaded boat, I usually throw a flotation bag in each end, even in a bulkhead boat. It's good backup, if you are of the 'belt AND suspenders' mindset. Cheap prevention of 'Cleopatra's Needle' syndrome.
I do have to remember to open the flotation bag valve after paddling - if it's a hot day the pressure in the bag can get high.