Considering how good cobia tastes. That's one heck of a testament to shark meat. Once you decide to keep a shark, remember that it should be killed immediately. After the fish is dead, remove the head and tail and allow it to bleed off the side of the boat. Once the fish is completely bled, put the fish in an ice chest.
Beer is another good marinade for shark.
It's also very good grilled with lemon pepper or garlic salt. My personal policy on retaining sharks depends on the species and the conditions of fish after landing it. In the past before I started using circle hooks, if the shark was bleeding profusely from the gills, it went in the ice chest. Using circle hooks will help avoid this problem though. Now I only take home a few small sharks a year to eat and leave the rest to proliferate in the ocean.