var x1=Math.floor(Math.random()*5)+1;
var x2=x1+1;
var x3=x1+2;

var y1=Math.floor(Math.random()*7)+1;
var sea=[
		 [null, null, null, null, null, null, null, null],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
];

sea[y1][x1]=1;
sea[y1][x2]=1;
sea[y1][x3]=1;

console.log(sea);
console.log(x1,x2,x3);
console.log(y1);