Investigate tanker is a mission in Daxter. After taking out a hive queen in Emerald Isle, Osmo called Daxter and told him to return to the tanker in the Port. Partially through the mission, Daxter accidentally breached part of the ship's cargo storage and was caught in the resulting explosion. The explosion ultimately led to him deciding to investigate the palace.
You start in the same room where you first met Tik. One doorway was left unexplored previously; enter here and hover over the dark eco that has flooded the hallway and take an elevator at the end. The elevator takes you to the deck, in the midst of a large pool of dark eco. Big bubbles will rise up periodically, but they are only dangerous when they pop, so do not bother trying to dodge new ones and watch out for the highest. Use wooden platforms in the pool to move around (new ones pop up as you get close to them). Otherwise, use gas clouds to hover around when necessary.
Continue this way, heating up a valve to drain a pool of dark eco and clear up a path, until you reach a trampoline. It takes you into smokestack where you must ride a platform across a long corridor, flooded with dark eco and a large number of broken pistons blocking your way. Balance the use of your spray gun's pressure boost attachment between flying over the pistons and killing any flankers in your way. Soon enough you will have to heat up another valve which trigger's an alarm and a two-minute timer.
You must now hurry down a zip line, onto a trampoline and back to the deck of the ship. Race across wooden platforms while dodging flankers and the dark eco below. At the end you must heat up a valve which drains the dark eco, allowing you to enter a room below. Drop down a hatch in the back of said room to safely escape the ship.