Questions about creating stuff

Hi! I have started playing Sibnautica some hours ago and I have a couple of questions:

1. Waterproof lockers are supposed to stay under water? I created one further from the life pod thinking that I would just see it easily at surface level, but it sank and I completely lost track of where it was after exploring around for a bit, forever missing.

2. I've been getting messages from other pods and from a the Sunbeam ship. I got a message from pod #6 saying there’s radiation around. So far I've just found other 2 pods, both empty and destroyed, so I shouldn't waste resources on an extra radiation suit expecting to helpany survivors, right?

3. I don't know where I got them, but I have blueprints on my pda to create structures (floors, windows, etc), how can I create this and where is it intended to go? Is it meant to be built around the lifepod? Because I'm seeing there are blueprints for lockers and I would love to have those.

4. What do I need to or how do I identify or hatch alien eggs (or whatever it is that you do with those)?