Not exactly a shot of the tarp, but the only pic I have currently. The slip was 20' X 30' and accommodated 2 boats. So one Saturday, my slip neighbor and I, using step ladders, strung a 20' X 30' tarp up by its grommets and then supported it further by running rope back and forth underneath to prevent pooling of any moisture that might somehow end up on top of the tarp, in case the metal roofing leaked some. It put an end to everything nasty falling on the boat and mooring cover. Congrats to Bama...again.
I will be hanging blue tarp similar to this over my Bennington in my covered boat slip on Lake Martin.
I will post any reduction in the dreaded spider poop

Over the last 20+ years on the water I have learned a few things about boat insect problems... not to be confused with any scientific studies
- Moth Balls do prevent some insects from entering under your boat cover - especially Dirt Daubers (common when red clay mud is available)
- Dryer Sheets work best only inside closed compartments and small areas
- Mooring covers may cause some degree of mildew
- Outdoor Lights attract insects and spiders must eat to live
- One spider in your boat can hatch 100s of little spiders in a short period of time
- Birds hate netting ( black fabric netting like chicken wire ) can reduce nesting birds when hung in boat slip rafters
- Plastic snakes can deter birds especially on exposed extended aft decking - rotate snakes for best effect - pop up cleats are best since there’s no bird perch when down.
- Mice are only a problem if there is a food source
- Ants will board your boat via dock lines or lift cables to find any amount of spilled soda or watermelon juice
- Ethanol will never be used in my toys
Just my 2 cents and not all inclusive - Enjoy the water!