*Digs up old thread*
Most modern surfing and triathlon wetsuits are already essentially airtight across all seams. People don't like cold water flushing in and out as they bend their arms and legs, so the suits are already designed to not do that.
If a wetsuit has a smooth slick exterior like a triathlon suit, at the wrists and ankles, then you don't necessarily even need dry seals. Just get a taller suit than you need, tuck in and roll the end of the sleeve inward, and the smooth exterior will now seal against your skin.
The main problem with turning a wetsuit into a drysuit is the way the zipper and neck seal are installed. Back zip wetsuits are going to be just about impossible to modify this way, because the dry zip is not usually designed to separate on one end and seal very well, and neck seals are not designed to be split open and yet still seal tightly around your neck.
The modern super-stretch zipperless neck-entry wetsuits do a very good job of stopping cold-water flushing, but the tiny neck opening also needs to stretch large enough to the outside diameter around your neck and one of your shoulders. No drysuit neckseal is going to handle that without tearing, and drysuit zippers do not stretch. At all.
About the only options for a wetsuit to drysuit conversion are the usual stiff inflexible waterproof zipper locations:
- Across shoulders, front (restricts arm motion, bunches up around shoulders)
- Across shoulders, back (restricts arm motion, bunches up around shoulders, can't put it on or get out alone)
- Up one side of chest, around neck, down other side (Unisuit Exclusive, restricts stretching suit neck area open to get your shoulders in/out)
- Diagonal front (restricts lifting up one shoulder/arm overhead, bunches up across crotch where it folds when you sit down)
- On a hooded wetsuit, zipper straight up the back, up to the top-back of the hood (now you can't turn your head to the side, or even really look up and down very far, because of the rigid zipper on the back of your neck)
- Down the crotch, between your legs, and up the back (classic Unisuit, okay all-around flexibility, but forget about getting into it alone)