remove minion
paint sub shape , I use gray base . add a yellow overlay then clip minion middle bits to create base of sub.

cut out glass , duplicate 3 times and set as portholes.

bubbles : use round brush , add gradient overlay , fill new layer with black , set layer mode to colour dodge and paint yellow highlights. lower opacity . paint a little in the bubble with brush flow at 15% to add a little glow to the whole bubble.

liquefy the green to create plants. invert colour to get purple plants.

Rocks.. paint a rock shape. clip some of the mid ground background to the rock shape and use dodge /colour burn to create rocks.

window fill is created the same as bubbles. use a light blue , lower opacity so that you can see through. (I used two goggles for each window.. paint over the eye piece, place minion , then cover with another eye glass. layer mask out the eye piece. fill with light blue ,lower opacity , colour burn the edges and add a white highlight.

rivets . create round brown dot. add bevel then duplicate heaps of times and place where needed.

Top piece of sub is created same as base.. paint gray tower, clip minion to tower. add rivets.

FINSIHED LAYER was the yellow minion middle piece set to overlay with opacity set to 45%