A system wherein cold water from near the sea floor is pumped through a primarily vertical pipe (12) to a body (14) floating at the sea surface so energy can be obtained from water temperature differences. A pump (50) located at the bottom of the pipe, is part of a pump module (46) that can be inserted and removed horizontally through a slot (44) in a bottom structure (22) lying at the bottom of the pipe. The top of the pipe is sealed to a movable pipe connector, by a U-shaped elastomeric seal (110). The pipe can include a short top pipe section (126) and a long bottom pipe section (127) of smaller diameter (D), whose upper portion can be pulled up through the top pipe section when the top pipe section is damaged.