Wut?
A vent hose long enough to go from that fitting to loop around the top of the shock (zip tie) should be enough for almost 3 FEET of water crossing. You can get a low pressure check valve for that purpose, but seems over kill to me. Look in Off-road Jeep stores, Grainger, McMaser, Fastenal, Napa, Ace, for a 3/8" 2psi check valve.