A few hours late here, but this is my procedure for liquid intrusion into any electronics. Kinda reflects the advice from the sage people here.
First kill the power as fast as you can. Pull the battery or the cord. If it's wet inside it may have already gone to electron heaven but don't linger on your demise, it may be just on the edge of crapping out.
Liquids seem to have an easy time getting into the guts of things but trying to reverse that is almost impossible before damage due to corrosion occurs. You have to bite the bullet and disassemble it the best you can. Pop the case open or split the unit so the majority of the PCBs and inner workings are are exposed. You cannot dry anything out by the way it got inside in the first place.
Now what liquids have intruded is the next question. Clean water water is not a problem. You say it was dirty water. How dirty and with what? If after drying out it leaves a little crust or some mung on the board as long as it is not corrosive to the innards it may be of little concern. Now I do get calls for hits of coffee or coke. That now is a code three rescue.
If you decide that the inside needs to be flushed to rid it of anything that might cause damage just go ahead and do it. I second and third the use of alcohol to wash the board and components. It will help disperse water and flush out contaminates. 99% isopropyl is best, but heck denatured or even 70% isopropyl is better than the alternative. Clean water works too especially when coke or coffee is the culprit. Distilled is best but my bottle of drinking water has been pressed into service when I'm in the field. Very few things can be damaged by water. The speaker was mentioned so watch for those type of things.
If need be a cleaning agent can help dislodge the crud. A drop of dish soap or a very light spritz of simple green can get things moving as long as you rinse well. Using a small brush to work into the components and all the nooks and crannies is very helpful. Pay attention to LCD displays, large IC's or anywhere moisture can hide behind.
Now that you have a clean and rinsed and very wet device you need to dry it as quick as you can. There are numerous ways to do this. What I don't recommend is a bag of rice, or flour, or wheat chex or anything of the sort. It just takes too damn long. Kind of like watching paint dry.
You need warmth and air flow. My favorite is to start the car, turn on the defroster to high and stick the unit right over a vent on the dash. Turn it often like you were roasting it on a spit. Fifteen to twenty minutes later the device will be very toasty warm and dry. The next best would be outside in the direct sun and fresh air for at least an afternoon. Lastly a hairdryer if you're careful not to get it too hot.
Hope you are successful in the rescue efforts.