The ALU back-end is made for deeper diving...
On the the Gavin site (
Exploration, sea scooters. Fort Lauderdale, FL.) is info for the PVC and HDPE back-end(s):
On all versions of the scooter, the motor seal becomes at risk beyond about 550 feet, the bodies are subject to bowing at 700 feet and crushing at about 1100 feet.
In both the HDPE and PVC (nose and tail material) versions, the flex will become an issue in the 900 foot range, which becomes a moot point due to the risk to the seal and the chance of leaking around the o-rings if the body flexes (a major issue at all depths with HDPE bodies, which we do not use for that reason).
Between 450 and 650 feet, the flex in the PVC bodies is between 5/100 and 8/100 of an inch.