The right approach when it comes to these pumps is getting one that comes with a flotation device that automatically turns the unit on when the situation requires it. Plus, the answer to this question depends on other factors as well. If there is no water accumulated in the bilge, then there’s no need to turn the pump on.
On the other hand, if water does accumulate in the bilge, the first thing you should do is figure out what the cause is, in case there’s any boat damage you should know about. Keep in mind that the goal here is to keep the bilge as dry as possible.