I recommend using the prawn suit alone since that's what i did for both of my 2 playthrough's (although driving it all the way from the bkz to the lost river to the ilz and to the alz was a bit painful, although very scenic).

Swim fast and get a cyclops thermal module. I don’t know where it is. You can also get a base really close to lava to use thermal reactors and inside the base have a power cell recharge station for the cyclops.

I recommend using the shield it uses alot for power but it stops damage and deflect lava leaches off ya and get the thermal reactor along with the sonar those 3 upgrades should be useful getting by Also pack spare power cells just incase