.pond {
    width: 350px;
    height: 300px;
    background-color: rgba(20, 61, 116, 0.548);
    background: linear-gradient(173deg, rgba(20, 61, 116, 0.548) 0%, rgba(4, 4, 17, 0.541) 55%, rgba(4, 4, 17, 0.63) 100%);
    position: relative;
    border: 5px solid rgb(43, 43, 43);
    border-radius: 130px;
}

.fish {
    width: 50px;
    height: 25px;
    position: absolute;
    opacity: 0;
    border-radius: 25px 35px 15px 25px;
    left: 50%;
    bottom: 50%;
}

.tail {
    position: absolute;
    width: 15px;
    height: 18px;
    left: -7px;
    top: 3px;
    border-radius: 0 20px 20px 0;
}

.wag {
    animation: tail-wag .25s ease-in-out 1;
}

@keyframes tail-wag {
    from {
        transform: rotate3d(0);
    }
    33% {
        transform: rotate3d(0, 1, 0, 45deg);
    }
    to {
        transform: rotate3d(0, 1, 0, -45deg);
    }
}