HOUSTON – Each attempt by a boat burglar is both clever and calculated.
"It kind of leaves your eyes open at night just waiting for him to come back," boat owner Blake Sullivan said.
A single kayaker, wandering the waters of the canal, seems to be up to more than just a cruise.
"Then he simply comes in and tries to destroy everything he can," Sullivan said.
For the past six weeks, Blake Sullivan says, the man in this video has brought quite a bit of concern to the Clear Lake canal.
"We've been leaving our boathouse lights on. He's gotten to the point now where that doesn't seem to faze him," Sullivan said.
Sullivan says the man in the gas mask is responsible for stealing not one, but four GPS units from boats docked in the harbor -- each worth up to $25,000. On Thursday morning, he tried to take Sullivan's.
The surveillance video shows what happened.
[WATCH: Boat burglar surveillance video]
"He sprayed a fire extinguisher on that camera and then worked his way to the back of the boathouse and sprayed a fire extinguisher on that camera," Sullivan said.
But unknowingly, this time, be left behind a small window into his crime.
In each case, the unwelcome boater doesn't just take the pricey navigator, but also destroys the vessel left behind with tools he brought with him.
"After that, he sprayed the boat down with bleach, acid, as well as the fire extinguisher to cover any traces of fingerprints," Sullivan said.
Because of his newly installed security guards, the man didn't actually kayak away with the GPS this time, but Sullivan says he'll be back.
"He'll notice the locks I had on there. Either possibly bring some type of tool to break the locks or remove the hinges. He's pretty diligent in trying to get what he wants," Sullivan said.
The damage from the acid will set Sullivan back nearly $3,000.
If you have any information on who this man might be, you're asked to call League City police.