:exclamationMost lakes have thermoclines at different depths.  If you can get below the thermocline the water will be 4 deg C at all times and can really cool off your drink.  The thermocline will shift with depending on the wind state but can be as shallow as 10 feet if the lake has been cold.  As far as drinks go however most good bar drinks require ice unless you go for the hot drinks like toddy's and buttered rum. I own a nightclub and its amazing the new stuff people keep coming up with.  Some of your cream drinks don't need to be cooled as much.  I enjoy many of the coffee drinks in the evening like Keoke, or Kahlua coffees or coffee with Bailey's also many of your stouter beers can be adequately cooled in the water or by wrapping with a cotton sock and allowing the wind to drop the temp.  Many of the really malty heavier bodied beers are frequently drunk too cold in the US (at least in my opinion) so that the true flavors don't get a chance to come through, a good malty beer really should only be around 40 deg F. One other thought is the chemical freeze packs available at hospital supply houses, they'll get your beverage down a few degrees especially if you place the bag and the beverage in a tight and well insulated container together. There are battery operated devices that will freeze on one side and heat on the other available from some of the electronic supply houses but I've never fooled around with one.  I enjoy a drink socially every once in a while but I am pretty much a teetotaler  when I am out in the wild. I use the experience to cleanse my mind, my body and my soul. Check out the "Old Mr. Boston" bar tender's guide, its still one of the best compilations of drinks in the busiess and always available behind my bar for reference: there is always someone coming in for a drink I've never heard of.