Does anyone know of an 80′s or 90′s movie?

I think its a comedy movie, its about some young guys that are looking for treasure under the ocean. There’s also an old guy that is with them that wears a dark coat and sunglasses and he’s kind of cookoo, but he’s funny. Towards the end of the movie the cookoo funny guy goes into the ocean and walks underwater after the guys find the treasure.
Please help! I can’t stop thinking or looking for this movie!!

Weekend at Bernie’s.

The guy wearing the dark coat and glasses is Bernie, and he is dead.

Underwater Treasure Hunting

Treasure Tracker $29.98 Hunt for coins, watches, jewelry and more with your very own Treasure Tracker digital metal detector! Explore the science behind searching for valuables at the beach or in your own backyard! You’ll be amazed what you can find buried right beneath you. Adjustable settings, a digital backlit display and audio tone alerts make this metal detector easy to use and provides hours of fun! You’ll never know when you could strike it rich!

Find It Sports Game $19.99 Find It is a totally contained 3-D Treasure Hunt. No batteries, buzzers, or beepers; just a good old-fashioned parlor game. The game is designed so that it can be left out on the coffee table, waiting room, desk as well as being the perfect travel game. Find It is a completely contained adventure;

Dragonblade: Cursed Lands Treasure $9.95 For thousands of years dragons' treasure lays in a temple in Cursed Lands… For thousands of years daredevils come searching for it…. For thousands of years they find final rest in Cursed Lands… … until the day White–Haired One will come. Dragonblade: Cursed Lands' Treasure is both fairy and scary tale. The Hero wakes up on the unknown coast and the only thing that explains his presence there is a shipwreck glittering in a distance. Quickly he finds out that…

Dead Man’s Treasure $3.99 A game of buccaneers and buried gold. It’s strategy and terror on the high seas as you seek out the Dead Man’s Treasure! Players compete to gain the most valuable treasure on a chain of six islands. Deploy your crew secretly to the islands in your quest for the loot, but watch out for booby traps, lest you find yourself on the bottom of the briny deep. Game includes 6 islands, 2 pirate pawns, 20 treasures, 40 pirate cards and instructions in English, Spanish and French. Game takes approximately 20 minutes to play. For 3 to 5 players. Ages 8 and up.

Titanic – Underwater Operation Simulator $19.99 Explore a legend! Switching places with a specialist on the submarine "Nephron", you now can explore the long lost wreck of the Titanic 4000 meters under sea level. Experience exciting adventures in a highly detailed and realistic 3D–deepsea–world and find out new and interesting information about the legendary Ocean liner