My Cumberland Float Tube has a leak....

My Classic Accessories Cumberland Float Tube I notice the air went down in one of my bladders when I used it this last weekend. This is only the 2nd time out in it. There is no puncture holes in it but I hear a hiss sound when you press ever so slightly on the valve ( see video). Is there anything I can doo to make it more sound? ( some type of caulking or patching or ?)....

Boston valves on the Cumberland have been known to be tough to seal . Most of the time they just need to be super clean and real tight. Take it all apart and wipe it off with a little alcohol and try again. If it’s not in the valve itself it might be where the ring seats on the bladder. You could try a little HH-66 pvc cement around the edges of the ring

BigMaxFloats -
Thank you for the info , I'm going to do what you suggest and I will post the end results next time I go out ....!