There really is not a product that I would consider safe to use around marinas. "Less toxic" might be a proper term. Essentria IC 3 is probably one of the only products that I would consider using in a misting system around a Marina with lakeside access. However, the problem is unless you have a system that agitates the chemical on a daily basis such as the Mistaway Gen 1.3, Essentria will separate in the tank. Essentria needs daily agitation and even agitation prior to misting. Its like mixing oil and water. It separates. There are not any other options that I would consider. Naprovite is an option that could be used around water, however my customers are mixed on the results and it is for Mosquitoes, not spiders. Wished I could give more info. Hope this helps.