My question might sound weird. I intend to participate in a 25k race at the beggining of June. It is in Spain and water tempreture would be about 21 deg. I generally swim in the mediteranean (and in the pool) in warmer water. I swam at about 20 degrees in the past; my longest swim in cool water was a 10k race ( about 21 deg ) and it felt ok without a wetsuit. (Swimming was fine; stopping to feed was cold) . Wetsuits are allowed and I can decide wether to use it or not in a few month but I'm not sure I can really anticipate the feeling of 8-9 hours in cool water . (I guess my longest swim would be about 17 k - 5-6 hours). Would it be wise to buy a wetsuit and use it anyhow ? I prefare swimming without it if it is a reasonable option.