2018
As a practical demonstration of this capability , we printed at sea underwater pressure housings that remained sealed to 200 m water depth with functional integrated internal electronics .
 As, underwater pressure housings, water depth, integrated internal electronics
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 As, underwater pressure housings, water depth, integrated internal electronics