[unirdna]

Yeah, air becomes about 10% less dense per 50 degrees F.

But, you shouldn't have to be reinflating "throughout the day". One "top off" should do it. The riffe float can be overinflated by 6 lb (human lungs can do about 2 lb). So, you can blow like hell and get it completely tight. Then when/if the float hits the cold water, the bladder still stays tight (despite the slight drop in air density).

So, to answer your question, "no", the flag never went limp despite the water temp being 55F. You can see in the photo the size of the disk at the base of the flag - about 3-4 inches. It's thick, firm rubber, and gets held in place firmly by the "riffe saddle".