let's hear your solution.
I have used several spray products over the years. When I leave the boat I lightly spray the dock lines and fenders in hopes of keeping the critters at bay. The trick is finding the right product. I came across it, called Bugtek. https://ca.binnacle.com/p13290/Bug-Tek- ... _info.html
Water based and once hit they die in seconds. My technique is to go out with my flashlight when it's dark as this is when they spin their webs and await their pray. A little shot of this stuff is all it takes. Along with treating deployed dock lines and fenders and spider hunting a couple of times at the beginning of the season, I normally remain entirely spider free for the rest of the season.
That being said, the spider issue is always outside. I have seen a spider once in a blue moon inside the boat but definitely not an issue.
A little about Bugtek. It is water based as mentioned, does not leave any trace after spraying anywhere including windows, gelcoat and canvas. Spray it on your hands and no residue or sticky feeling, just as if you sprayed water. Saw the product on demonstration several years back, salesman claims it is non toxic so he sprays it into his mouth and swallows.
I would never do that but I swear this is what he did. I use it quite often on plants around my home to control insects especially all the indoor plants. Great product. 
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