I would not reject either the salt water lake wood nor the less than clean water lakes. Really any wood can be considered usefull if treated right. Local wood can be found that works fine. Depending on the weather, it can be hard to find the good solid stuff that has dried fully. Wood in piles which are on the ground often get bugs and turn to mush before they dry. Sometimes one can find downed trees where the branchs are left in the air and bug free. Bugs are not the problem as a bleach soak will do them in but they tend to eat the fiber and leave a useless pulp. Storm areas or bulldozer piles??
Salt is not really a big problem as it is pretty diluted. Dirty water may leave good wood but I always do a bleach soak on any decor that goes in the tank. I like the idea of KNOWING the wood is safe rather than guessing.
A tub of water to fit the wood with a 1/2 cup or so of cheap household bleach without scent like lemon, will do the disinfection and cleaning to assure there is nothing on the wood. Otherwise oils or pesticides may be soaked in the wood. Boiling does not remove oil. When done soaking like overnight or longer, wash the bleach water off and let it dry. The chlorine is a gas by nature and will blow away during drying. Ever smell chlorine around a pool? That is the chorine blowing away. Drying may take longer than the soaking but a nice sunny spot on hot concrete will speed it up.
Look to the driest wood to be found to avoid fighting tannins.