Lockers can be attached to the walls of all of the base parts as far as I know. They can be installed in the tube-like section, the X-section and the rest. Never tried to put them on glass though. Anything you build can be quickly undone and you recover the mats. So you're free to experiment, or to build in one place, then pack it up and build it somewhere else.

Gasopods are those manatee-looking things yes. If you're quick you can simply grab their gas sack before they explode. Once you have a Sea Glide you can just zip away at the first sign of trouble. Crash fish evasion.