On water emergency services will be provided by Larimer County Dive Rescue or Coast Guard staff in zodiacs and Park Rangers in power boats. EMTs from Poudre Valley Hospital will be in attendance. They will be ready to treat cold and water injuries in addition to their normal care.
The EMT's will be at Satanka Cove at the north end of the lake. There will be multiple Dive Rescue boats on the lake looking for people in trouble.
Spectator boats for any of the races will not be allowed to follow "their" swimmer on the course. They can follow them from a safe distance beyond the race course (behind safety canoes/kayaks), but will not be allowed to follow next to the swimmer they are watching.
10K Swimmers must provide or pay for a support craft. Each 10K swimmer is required to have a support craft during the race. A support craft consists of a kayak or canoe with a paddler who accompanies the swimmer for the duration of the event. Swimmers have two options:
For the 10K race only, a support craft is required for several reasons. Some of these are:
For all other races (2.4 & 1 mile, 250 & 1000 yards), the race committee will provide safety boats.
The biggest challenge that a swimmer will have at the Horsetooth Swim is handling the colder water for the extended period. Being a high altitude lake, the water temperature stays relatively cool year round. At the time of the swim, it typically warms up to 65-70F. To complicate things, we abide by international rules for long distance swims where wetsuits are NOT allowed (for the 10K).
In our experience, the cold water is the biggest challenge endurance athletes have to overcome. We are not sure how you will get acclimated to the cold water but we will warn you to take the temperature seriously. In 2002, despite the much publicized drought we were experiencing, the water temperature dropped to 62F for the swim. None of the locals had been training in cold lakes since all the lakes were warmer then normal due to the drought. The colder temperature in Horsetooth still remains a mystery to us even though we have some theories. Anyway, the result was a record number of DNFs due to the cold temperature. The medics had to treat two cases of hypothermia. Unfortunately, we do not have control of the water temperature.
Even in 2008 with the water temperature in the 70s, we had swimmers that did not finish the race due to hypothermia.
Some information on hypothermia is available at hypothermia.org as well as from the University of Minnesota (which covers hypothermia in water very nicely).
Swimming Induced Pulmonary Edema (SIPE) is a fairly rare condition. It is similar to High Altitude Pulmonary Edema (HAPE) that is well known to moutaineers. In both cases, fluid fills up the lungs. In these cases, the fluid is not from an external source, but rather from the blood vessels themselves. If enough fluid collects in the left lung, it will start to prevent the heart from beating as normal. This is a medical emergency. If this happens, the swimmer should stop as soon as possible and get Dive Rescue and/or the EMTs to them as soon as possible. The "good" news is it's pretty easy to detect. A swimmer will mostly likely be coughing and spitting up a pink frothy sputum as well as complaining of shortness of breath, note that chest pain is not a symptom.
US Open Water Swimming has an article on it. Two others are available here and here.