Dog/snake hybrid monster

Today Cyclops and I went a little trip out to Ullapool and to Gruinard Bay which it is claimed has pink sand although actually its more... well a dark sandy colour.

Later in the bay by the house we saw an animal in the sea but we're not sure what it was. We watched it for ages and it kept going underwater for a few minutes then coming back up for a breather with its head facing upwards, then repeating and coming back up in exactly the same place. It was vaguely seal-like but not behaving seal-like. I think it was a dog/snake hybrid monster. I'm pretty sure it was that there is no other logical explanation.