Crispy Coconut Shrimp with Pineapple Relish

1 pineapple peeled, cored, cut into 1/4-inch cubes
1/3 cup of finely chopped red onion 
1/4 cup of finely chopped red bell pepper 
1 jalapeno pepper, seeded and minced
1 tablespoon of fresh lime juice 
1 tablespoon of chopped fresh cilantro 
1 teaspoon of sugar 
3/4 teaspoon of salt divided
2/3 cup plus 2 tablespoons of all-purpose flour divided
1/2 teaspoon of baking soda 
1/4 teaspoon of cayenne pepper 
2/3 cup of seltzer 
1 large of egg 
3 1/2 cups of sweetened shredded coconut 
40 extra large of shrimp about 1 1/2 pounds, peeled, deveined, tails left intact
7 cups of canola or peanut oil

1. Combine the pineapple, onion, bell pepper, jalapeno, lime juice, cilantro, sugar, and 1/4 teaspoon of the salt in a bowl; reserve.
2. Combine 2/3 cup flour, baking soda, the remaining 1/2 teaspoon of salt, and cayenne pepper in a medium bowl. Add the seltzer and egg and whisk until smooth. Place coconut in a separate bowl.
3. Heat the oil in a large heavy pot over medium-high heat until it registers 350°F on a thermometer. While the oil heats, working one at a time, hold the shrimp by the tail and dip it into the batter; shake to remove excess, and dip into coconut to completely coat it, pressing gently to help the coconut adhere to the shrimp. Transfer to a baking sheet and repeat with remaining shrimp.
4. Add shrimp to the oil in batches of 8-10 and cook until golden brown and crisp, about 1 1/2 minutes. Remove shrimp from oil with a slotted spoon and drain on paper towels. Skim any coconut from the oil, return to 350°F and continue frying. Serve with pineapple relish.