My take on the marine alien lifeform is that, it uses radiation beams as sonar/echolocation. This is seen to cause the radiation spikes and warmth of the oceanic area detected by the satellite causing the first mission. My hypothesis on why the ship crashed when trying to take back off is due to them attacking the ship. The alien(s) squid interpreted the bright, vibrant exhaust flames as an attack and they retaliated with a bombardment of radiation. The increased radiation surge, fried key computer systems, causing two of the four rockets to fail, forcing a survivable hard landing via water shield sacrifice (main ship radiation protection and heat source).