Ephesians 4:27 Neither give place to the devil.
When unmarried couples share a tent for the purpose of sleeping together while camping, are they not "giving place to the devil"? Does this not open the door for temptation? Did Jesus not say, in the "model prayer" (Matthew 6), "lead us not into temptation"? In James 1:13-16:
James 1:13 Let no man say when he is tempted, I am tempted of God: for God cannot be tempted with evil, neither tempteth he any man:
James 1:14 But every man is tempted, when he is drawn away of his own lust, and enticed.
James 1:15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.
James 1:16 Do not err, my beloved brethren.
If you play with fire, sooner or later you will get burned.