I built the Aero RAF Fire Tender back In 1972, I was In the RAF during the 60's. After a year of regular use, It ended up In the loft and my working life took over for the next 25 years or so.

I restarted the hobby and recovered the model from the loft, completed a refit with a new 5cc IC engine and modern Radio gear.
Keen to test the boat. I took It down to the River Arun In West Sussex. However I found the river In flood but unwisely continued to put the boat on the water. She performed nicely, until the prop hit an object and the motor cut. The boat soon drifted to the middle of the fast flowing river and started off downstream. After a few hundred yards I decided to swim out and retrieve the boat, somewhat ahead of It. No problem with that, as I though I am a strong swimmer. I got hold of the boat no problem, then attempted to swim back to shore. However at this point In the river, It narrowed and hence the flow rate Increased somewhat. With the boat In hand, I found It Impossible to swim back to shore and eventually tired and had to rest.
It was at this point, I found the model provided enough buoyance to help keep me afloat. I drifted downstream holding onto the boat for about a mile, before an elderly gentleman seeing my plight, found a broken branch, long enough for me to get close enough to and eventually back to shore.