These are like many toolbox latches. I agree that they can pop open. They also usually loosen up over time.

A variation that may be more effective can be found on work trucks with side tool boxes. Take a look at these because they get bounced around a lot. They also usually rattle-but if you've got weather stripping on your hatch that should dampen any rattling (and I've never seen a pothole on the ocean.)
I think many deck hatch hold downs seem to work sideways rather than down.They must work or we'd be hearing about them.
Also keep in mind it was the deck hatch hold downs that doomed the Edmund Fitzgerald.
Will

: They look the same as the DAXX ones on my hinge templete tool box. I have
: lost count how many times the FXBFSSE thing has droped open on me. I think
: with the hard deck they will work better but if you ever have put a body
: on the deck they will bite, maybe reccesed would do and look cool.
: Don