"swimming" condition to activate an effect

I created a similar thorn enchantment but with activation of the dolphin effect for a few seconds for those affected. The point is that I would like this feature to be activated in water or at least while swimming (Although simply activating it when in water would be better). I honestly don't know how to do it I had some ideas but it doesn't look decent.
code:
{
    "description": "Dolphin Call",
    "supported_items": "#minecraft:enchantable/chest_armor",
    "weight": 1,
    "max_level": 3,
    "min_cost": {
        "base": 15,
        "per_level_above_first": 9
    },
    "max_cost": {
        "base": 45,
        "per_level_above_first": 9
    },
    "anvil_cost": 4,
    "slots": [
        "chest"
    ],
    "effects": {
        "minecraft:post_attack": [
            {
                "enchanted": "attacker",
                "affected": "victim",
                "effect": {
                    "type": "minecraft:apply_mob_effect",
                    "to_apply": "minecraft:dolphins_grace",
                    "min_duration": {
                        "type": "minecraft:linear",
                        "base": 1,
                        "per_level_above_first": 2
                    },
                    "max_duration": {
                        "type": "minecraft:linear",
                        "base": 1,
                        "per_level_above_first": 2
                    },
                    "min_amplifier": 0,
                    "max_amplifier": 0
                },
                "requirements": {
                    "condition": "minecraft:random_chance",
                    "chance": {
                        "type": "minecraft:enchantment_level",
                        "amount": {
                            "type": "minecraft:linear",
                            "base": 0.15,
                            "per_level_above_first": 0.15
                        }
                    }
                }
            }
        ]
    }
}