There are nice Colgates for rent from "Mohammed" on the corniche. You can't miss them, there are about 6-10 of them - all sail boats that easily accomodate 4 adults. Just near to the old cafe were all the older generation Qataris hang out. Look out for them and find somebody nearby to direct you to the owner, some of them have a mobile phone number of the side to call.

Best of Luck,