My decked boat is upside down under four feet of snow so no pics now. Make a raised lip with Trex plastic fascia or decking boards. Make the lids out of plywood or honecomb core, with Trex edges that fit over the raised lips in the deck. Glue foam to the inside of the lid with barge cement. Epoxy goo adheres well to plastic fascia board if you rough it up with sand paper first.
Stainless hinges on one side. Spring loaded pull down wire clasp latches on the other edge, that pull the lid down tight. Down tightly is the key. I had to use hard plastic shims under the hinges to fine tune it, so the clasps pulled down evenly all around. Do that and it is water tight.
The clasps I bought are springy stainless wire you adjust by twisting the clasp before snapping it down. Round flush latches are useless. You need a wrench to adjust them. They don't pull down tightly and they leak.
These are similar to what I bought. Not exactly the same but similar. You need quick easy adjustment, no matter what. What's tight today is loose tomorrow.
https://www.amazon.com/a16112200ux0606-Stainless-Holding-Capacity-Hardware/dp/B01MR2O2TF/ref=asc_df_B01MR2O2TF/?tag=hyprod-20&linkCode=df0&hvadid=241898984112&hvpos=1o5&hvnetw=g&hvrand=429605820243323623&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9021322&hvtargid=pla-535337366356&psc=1
