Gas tank issue at the pump

[Foul Hook]

My brother has issue when he fills his tank, the gas will bubble out of the fill hose and kick the pump off. We have taken off both the fill hose and the vent host to get a visual to see if they are collapsing or blocked. Both are good, clear and clean. The odd thing about this is that when we fill the boat at the pump or by can on land there is no problem filling at all. When filling on land we can hear the vent allowing air out. Put the boat in the water when filling the gas will keep bubbling out of the fill hole. Talked to the guy who cleans the tanks he says his services are not needed. Could it be that baffles are causing this problem? Any Thoughts? Thanks