This is actually an excellent exercise in physics and relativity. The gas , prior to expulsion, resides in the lower intestinal track. It is of a specific density and volumn. Therefore it has a measurable bouyancy index. Example, if you blow three times into a small balloon you have specific amount of air in a tight, confined area. If you put the same amount of air into a larger balloon, you stll have the same amount of air but in a less confined area. Once it is expelled into the wetsuit the only difference at this point is that the confined surroundings once containing the fart are no longer present. The volumn of gas is the same but in a much more dispersed condition. The permeability of the wetsuit comes into play at this point along with how tight the wet suit is.
Charles Lindburgh contemplated a similar question to kill time and stay awake when he made the non stop flight from the US of A to Paris. There was a fly in the cockpit of his aircraft and he wondered ....did the aircraft weigh more when the fly was flying...or did the aircraft weigh more when the fly was not flying? It has since been shown that the aircraft actually weighed more when the fly WAS NOT flying because when he was flying he exerted equal air pressure through out the cabin. When he wasnt flying his weight was directly in relationship with the aircraft at that point.
It would seem that the key and more important question would involve a Drysuit versus a wet suit. This is based on the permeability of the wetsuit versus the gas confining attributes of a dry suit.
Regardless of all the above....the most important point is....NO FARTS ARE NOT LUMPY..... You have just s***.
Once again proving....too much knowledge can be totally useless!!