The River Douro runs alongside the Ribeira District, UNESCO World Heritage Site, Porto, Douro, Portugal, Europe

Pastel coloured houses alongside a canal in Burano, Venetian Lagoon, Venice, Veneto, Italy, Europe

Trawlers moored alongside in the fishing port of Brixham, Devon, England, United Kingdom, Europe

King Edward Point research station with fisheries patrol boat Pharos alongside at the jetty, South Georgia, Polar Regions

Boat moored alongside house on the bank of the Canal du Midi, Le Somail, Aude, Languedoc Roussillon, France, Europe

The classic English village of Welford-on-Avon with the thatched Ten Penny cottage alongside Boat Lane, Welford-on-Avon, Warwickshire, England, United Kingdom, Europe

Fishing boat coming in to moor alongside other fishing boats and sailing yachts in Looe harbour, Cornwall, England, United Kingdom, Europe

A blue whale (Balaenoptera musculus) surfaces alongside a panga with tourists. The tiny dorsal fin is visible to the left of the white hat. Gulf of California. (RR)

Blue whale (Balaenoptera musculus) Gulf of California. A very relaxed blue whale surfaces right alongside a tourist boat, note the pronounced vertebrae.

Blue whale (balaenoptera musculus) A blue whale raises its tail alongside a tourist in a small boat.The Gulf of California.

Striped dolphin (Stenella coeruleoalba) leaping alongside boat, although the most abundant dolphin species in pelagic waters of the Mediterranean Sea the population is listed as vulnerable, North Aegean Sea, Greece. (RR)

A curious Bryde's whale (Balaenoptera edeni) swims alongside a boat. Gulf of California. (A4 only).

Visitors enter boats at Dasaswamedh Ghat alongside Ganges river, Varanasi, Uttar Pradesh, India

Crowds in boats admire evening Aarti prayer ceremony at Dasaswamedh Ghat alongside Ganges river, Varanasi, Uttar Pradesh, India

Cremation fire at Manikarnika Ghat alongside Ganges river, Varanasi, Uttar Pradesh, India

Hindu monk performs prayer ceremony at Dasaswamedh Ghat alongside Ganges river at sunrise, Varanasi, Uttar Pradesh, India

Pilot cutter alongside Cruiseship MV Columbus, Tonga, South Pacific, Oceania

Sightseeing boat Christl and buildings of Klein Venedig Little Venice district alongside the left branch of the Regnitz river, Bamberg, Franconia, Bavaria, Germany

Houses alongside a canal, Burano, Venice, Veneto, Italy, Europe

Pilot Boat alongside a Container Ship with a Rainbow, Victoria, British Columbia

Tiger shark;Galeocerdo cuvier) swimming alongside a boat to protect itself from killer whales;Orcinus orca), Mayotte