is there such a thing have searched with no avail,
my atlantic 21 is a wet deck as they all are, fitted a std hatch at rear for access to bilge pump, it lets as much water in as the bilge pump kicks out,
do not really need regular access in there, ideally want a sealed on base plate with bolt on lid
i could make some thing up and glass it into floor with big head fixings and gasket seal, or tapped 5mm ali plate but weighty.
but i find my self out of manual action for a little while and wish to go down the easy route if there is one
the base is smoothed under neath & silcoln sealed, then the non slip wash brushed up to it, simply the lid seal does not do its job well