Locate the gadget inside the McMarx Sports Shack

Locate the gadget inside the McMarx Sports Shack is a mission in Ratchet & Clank. Clank recommends that Ratchet investigate the McMarx Sports Shack to search for more items. After doing so, they obtained the Hydrodisplacer.

This mission must be completed to complete "Search the sewers" on Rilgar, as the Hydrodisplacer is required.

Walkthrough
Enter the McMarx Sports Shack using the same path taken in "Find Skidd's Agent". After taking the elevator to the Sports Shack, take the path on the left. Hold to use the Swingshot pull towards the versa-target, and then swing across the next versa-target to reach the platform on the end. Here, you must use the Swingshot to traverse several versa-targets, using it to pull towards them and reach different platforms and conveyor belts. Dropping to the platforms below allows you to destroy the crates for bolts before moving on.

Eventually, you will reach a large, round room, with versa-targets across to the end. Use the Swingshot to travel to the end, then use the Swingshot to travel up right twice. Once on a higher ground, use the Swingshot to reach higher ground and eventually enter the final room, with a platform surrounded by water. Picking up the Hydrodisplacer here allows you to connect it to a plug point and drain the surrounding water, then drop down to a bolt crank. Before opening the door outwards with the bolt crank, first swim down the remaining water using to reach the gold bolt below, then swim back up, turn the bolt crank, and leave through the door. Here, another plug is found. Plug the Hydrodisplacer in to refill this water, then swim across on the top to the end and take the elevator down.

If the remaining missions "Help Skidd get back to his ship" and/or "Find Skidd's Agent" are not complete, finish them before moving on to the next planet. If they are, with the Hydrodisplacer unlocked, you can fully complete Rilgar.